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 $116.91   7.773%   $125.9974   $126.00   $126.00   $126.00  
  Purchase #2 $203.79   11.758%   $227.7516   $227.75   $227.75   $227.80  
  Purchase #3 $54.72   6.462%   $58.256   $58.26   $58.25   $58.30  
  Purchase #4 $53.57   11.457%   $59.7075   $59.71   $59.70   $59.70  
  Purchase #5 $215.39   6.356%   $229.0802   $229.08   $229.10   $229.10  
  Purchase #6 $14.67   11.496%   $16.3565   $16.36   $16.35   $16.40  
  Purchase #7 $152.52   4.517%   $159.4093   $159.41   $159.40   $159.40  
  7 purchase totals = $811.57       $876.5585   $876.57   $876.55   $876.70