Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $118.74   6.628%   $126.6101   $126.61   $126.60   $126.60  
  Purchase #2 $249.85   13.303%   $283.0875   $283.09   $283.10   $283.10  
  Purchase #3 $195.62   5.250%   $205.8901   $205.89   $205.90   $205.90  
  Purchase #4 $142.52   4.793%   $149.351   $149.35   $149.35   $149.40  
  Purchase #5 $189.69   11.642%   $211.7737   $211.77   $211.75   $211.80  
  Purchase #6 $189.76   12.243%   $212.9923   $212.99   $213.00   $213.00  
  Purchase #7 $233.98   9.340%   $255.8337   $255.83   $255.85   $255.80  
  7 purchase totals = $1,320.16       $1,445.5384   $1,445.53   $1,445.55   $1,445.60