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 $53.92   12.615%   $60.722   $60.72   $60.70   $60.70  
  Purchase #2 $247.96   8.327%   $268.6076   $268.61   $268.60   $268.60  
  Purchase #3 $99.78   8.634%   $108.395   $108.40   $108.40   $108.40  
  Purchase #4 $64.69   11.237%   $71.9592   $71.96   $71.95   $72.00  
  Purchase #5 $13.72   6.149%   $14.5636   $14.56   $14.55   $14.60  
  Purchase #6 $59.35   3.542%   $61.4522   $61.45   $61.45   $61.50  
  Purchase #7 $236.69   6.112%   $251.1565   $251.16   $251.15   $251.20  
  7 purchase totals = $776.11       $836.8561   $836.86   $836.80   $837.00