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 $119.52   5.128%   $125.649   $125.65   $125.65   $125.60  
  Purchase #2 $211.78   7.793%   $228.284   $228.28   $228.30   $228.30  
  Purchase #3 $201.46   12.391%   $226.4229   $226.42   $226.40   $226.40  
  Purchase #4 $93.38   5.668%   $98.6728   $98.67   $98.65   $98.70  
  Purchase #5 $99.98   10.565%   $110.5429   $110.54   $110.55   $110.50  
  Purchase #6 $159.98   3.463%   $165.5201   $165.52   $165.50   $165.50  
  Purchase #7 $96.30   3.361%   $99.5366   $99.54   $99.55   $99.50  
  7 purchase totals = $982.40       $1,054.6283   $1,054.62   $1,054.60   $1,054.50