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 $48.86   9.575%   $53.5383   $53.54   $53.55   $53.50  
  Purchase #2 $219.90   12.405%   $247.1786   $247.18   $247.20   $247.20  
  Purchase #3 $12.31   7.408%   $13.2219   $13.22   $13.20   $13.20  
  Purchase #4 $235.95   3.579%   $244.3947   $244.39   $244.40   $244.40  
  Purchase #5 $126.55   6.732%   $135.0693   $135.07   $135.05   $135.10  
  Purchase #6 $214.58   5.314%   $225.9828   $225.98   $226.00   $226.00  
  Purchase #7 $155.26   12.688%   $174.9594   $174.96   $174.95   $175.00  
  7 purchase totals = $1,013.41       $1,094.3450   $1,094.34   $1,094.35   $1,094.40