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 $88.37   9.700%   $96.9419   $96.94   $96.95   $96.90  
  Purchase #2 $185.95   10.299%   $205.101   $205.10   $205.10   $205.10  
  Purchase #3 $55.54   3.843%   $57.6744   $57.67   $57.65   $57.70  
  Purchase #4 $49.86   3.561%   $51.6355   $51.64   $51.65   $51.60  
  Purchase #5 $84.25   3.386%   $87.1027   $87.10   $87.10   $87.10  
  Purchase #6 $179.47   4.684%   $187.8764   $187.88   $187.90   $187.90  
  Purchase #7 $60.49   12.616%   $68.1214   $68.12   $68.10   $68.10  
  7 purchase totals = $703.93       $754.4533   $754.45   $754.45   $754.40