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 $61.89   6.106%   $65.669   $65.67   $65.65   $65.70  
  Purchase #2 $118.28   3.450%   $122.3607   $122.36   $122.35   $122.40  
  Purchase #3 $159.93   10.832%   $177.2536   $177.25   $177.25   $177.30  
  Purchase #4 $101.41   4.599%   $106.0738   $106.07   $106.05   $106.10  
  Purchase #5 $210.82   6.232%   $223.9583   $223.96   $223.95   $224.00  
  Purchase #6 $111.87   6.162%   $118.7634   $118.76   $118.75   $118.80  
  Purchase #7 $237.66   12.844%   $268.1851   $268.19   $268.20   $268.20  
  7 purchase totals = $1,001.86       $1,082.2639   $1,082.26   $1,082.20   $1,082.50