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 $31.26   4.757%   $32.747   $32.75   $32.75   $32.70  
  Purchase #2 $235.43   3.362%   $243.3452   $243.35   $243.35   $243.30  
  Purchase #3 $230.84   6.819%   $246.581   $246.58   $246.60   $246.60  
  Purchase #4 $152.25   8.312%   $164.905   $164.91   $164.90   $164.90  
  Purchase #5 $72.80   10.261%   $80.27   $80.27   $80.25   $80.30  
  Purchase #6 $230.52   11.605%   $257.2718   $257.27   $257.25   $257.30  
  Purchase #7 $229.67   6.244%   $244.0106   $244.01   $244.00   $244.00  
  7 purchase totals = $1,182.77       $1,269.1306   $1,269.14   $1,269.10   $1,269.10