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 $210.93   10.302%   $232.66   $232.66   $232.65   $232.70  
  Purchase #2 $11.39   5.180%   $11.98   $11.98   $12.00   $12.00  
  Purchase #3 $168.38   3.277%   $173.8978   $173.90   $173.90   $173.90  
  Purchase #4 $248.57   3.709%   $257.7895   $257.79   $257.80   $257.80  
  Purchase #5 $164.55   3.441%   $170.2122   $170.21   $170.20   $170.20  
  Purchase #6 $155.66   11.397%   $173.4006   $173.40   $173.40   $173.40  
  Purchase #7 $97.25   11.170%   $108.1128   $108.11   $108.10   $108.10  
  7 purchase totals = $1,056.73       $1,128.0529   $1,128.05   $1,128.05   $1,128.10