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 $210.97   10.299%   $232.6978   $232.70   $232.70   $232.70  
  Purchase #2 $84.61   12.482%   $95.171   $95.17   $95.15   $95.20  
  Purchase #3 $148.38   8.635%   $161.1926   $161.19   $161.20   $161.20  
  Purchase #4 $118.81   4.411%   $124.0507   $124.05   $124.05   $124.10  
  Purchase #5 $126.47   12.637%   $142.452   $142.45   $142.45   $142.50  
  Purchase #6 $147.52   8.851%   $160.577   $160.58   $160.60   $160.60  
  Purchase #7 $46.38   5.587%   $48.9713   $48.97   $48.95   $49.00  
  7 purchase totals = $883.14       $965.1124   $965.11   $965.10   $965.30