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 $48.31   9.599%   $52.9473   $52.95   $52.95   $52.90  
  Purchase #2 $184.88   6.222%   $196.3832   $196.38   $196.40   $196.40  
  Purchase #3 $154.57   5.805%   $163.5428   $163.54   $163.55   $163.50  
  Purchase #4 $226.71   6.156%   $240.6663   $240.67   $240.65   $240.70  
  Purchase #5 $84.63   3.458%   $87.5565   $87.56   $87.55   $87.60  
  Purchase #6 $150.29   5.132%   $158.0029   $158.00   $158.00   $158.00  
  Purchase #7 $149.93   9.504%   $164.1793   $164.18   $164.20   $164.20  
  7 purchase totals = $999.32       $1,063.2783   $1,063.28   $1,063.30   $1,063.30