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 $41.72   11.855%   $46.6659   $46.67   $46.65   $46.70  
  Purchase #2 $141.57   13.106%   $160.1242   $160.12   $160.10   $160.10  
  Purchase #3 $88.66   7.274%   $95.1091   $95.11   $95.10   $95.10  
  Purchase #4 $152.29   7.368%   $163.5107   $163.51   $163.50   $163.50  
  Purchase #5 $60.92   6.355%   $64.7915   $64.79   $64.80   $64.80  
  Purchase #6 $153.63   3.257%   $158.6337   $158.63   $158.65   $158.60  
  Purchase #7 $92.41   5.520%   $97.511   $97.51   $97.50   $97.50  
  7 purchase totals = $731.20       $786.3461   $786.34   $786.30   $786.30