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 $118.56   6.319%   $126.0518   $126.05   $126.05   $126.10  
  Purchase #2 $33.52   8.290%   $36.2988   $36.30   $36.30   $36.30  
  Purchase #3 $210.94   11.140%   $234.4387   $234.44   $234.45   $234.40  
  Purchase #4 $221.99   11.693%   $247.9473   $247.95   $247.95   $247.90  
  Purchase #5 $178.39   9.200%   $194.8019   $194.80   $194.80   $194.80  
  Purchase #6 $73.66   7.162%   $78.9355   $78.94   $78.95   $78.90  
  Purchase #7 $202.33   6.867%   $216.224   $216.22   $216.20   $216.20  
  7 purchase totals = $1,039.39       $1,134.6980   $1,134.70   $1,134.70   $1,134.60