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 $62.61   11.297%   $69.6831   $69.68   $69.70   $69.70  
  Purchase #2 $138.83   3.472%   $143.6502   $143.65   $143.65   $143.70  
  Purchase #3 $204.69   7.209%   $219.4461   $219.45   $219.45   $219.40  
  Purchase #4 $147.97   5.501%   $156.1098   $156.11   $156.10   $156.10  
  Purchase #5 $54.42   10.486%   $60.1265   $60.13   $60.15   $60.10  
  Purchase #6 $247.51   13.290%   $280.4041   $280.40   $280.40   $280.40  
  Purchase #7 $28.50   12.275%   $31.9984   $32.00   $32.00   $32.00  
  7 purchase totals = $884.53       $961.4182   $961.42   $961.45   $961.40