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 $88.52   10.734%   $98.0217   $98.02   $98.00   $98.00  
  Purchase #2 $210.60   11.241%   $234.2735   $234.27   $234.25   $234.30  
  Purchase #3 $239.94   5.564%   $253.2903   $253.29   $253.30   $253.30  
  Purchase #4 $58.27   5.795%   $61.6467   $61.65   $61.65   $61.60  
  Purchase #5 $151.94   4.601%   $158.9308   $158.93   $158.95   $158.90  
  Purchase #6 $206.78   12.660%   $232.9583   $232.96   $232.95   $233.00  
  Purchase #7 $109.50   3.692%   $113.5427   $113.54   $113.55   $113.50  
  7 purchase totals = $1,065.55       $1,152.6640   $1,152.66   $1,152.65   $1,152.60