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 $166.50   5.673%   $175.9455   $175.95   $175.95   $175.90  
  Purchase #2 $68.49   9.469%   $74.9753   $74.98   $75.00   $75.00  
  Purchase #3 $176.64   11.185%   $196.3972   $196.40   $196.40   $196.40  
  Purchase #4 $247.93   11.809%   $277.2081   $277.21   $277.20   $277.20  
  Purchase #5 $26.64   11.723%   $29.763   $29.76   $29.75   $29.80  
  Purchase #6 $48.28   4.422%   $50.4149   $50.41   $50.40   $50.40  
  Purchase #7 $205.47   11.273%   $228.6326   $228.63   $228.65   $228.60  
  7 purchase totals = $939.95       $1,033.3366   $1,033.34   $1,033.35   $1,033.30