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 $200.69   5.794%   $212.318   $212.32   $212.30   $212.30  
  Purchase #2 $10.26   13.251%   $11.6196   $11.62   $11.60   $11.60  
  Purchase #3 $199.74   5.804%   $211.3329   $211.33   $211.35   $211.30  
  Purchase #4 $66.28   4.873%   $69.5098   $69.51   $69.50   $69.50  
  Purchase #5 $172.59   9.469%   $188.9325   $188.93   $188.95   $188.90  
  Purchase #6 $136.30   7.351%   $146.3194   $146.32   $146.30   $146.30  
  Purchase #7 $212.78   7.420%   $228.5683   $228.57   $228.55   $228.60  
  7 purchase totals = $998.64       $1,068.6005   $1,068.60   $1,068.55   $1,068.50