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 $94.33   7.618%   $101.5161   $101.52   $101.50   $101.50  
  Purchase #2 $156.29   4.774%   $163.7513   $163.75   $163.75   $163.80  
  Purchase #3 $5.31   13.710%   $6.038   $6.04   $6.05   $6.00  
  Purchase #4 $89.33   11.133%   $99.2751   $99.28   $99.30   $99.30  
  Purchase #5 $178.99   10.283%   $197.3955   $197.40   $197.40   $197.40  
  Purchase #6 $223.41   6.474%   $237.8736   $237.87   $237.85   $237.90  
  Purchase #7 $111.33   13.244%   $126.0745   $126.07   $126.05   $126.10  
  7 purchase totals = $858.99       $931.9241   $931.93   $931.90   $932.00