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 $110.88   4.635%   $116.0193   $116.02   $116.00   $116.00  
  Purchase #2 $136.42   3.868%   $141.6967   $141.70   $141.70   $141.70  
  Purchase #3 $54.51   6.332%   $57.9616   $57.96   $57.95   $58.00  
  Purchase #4 $138.44   11.125%   $153.8415   $153.84   $153.85   $153.80  
  Purchase #5 $92.27   4.190%   $96.1361   $96.14   $96.15   $96.10  
  Purchase #6 $153.47   3.229%   $158.4255   $158.43   $158.45   $158.40  
  Purchase #7 $8.91   9.342%   $9.7424   $9.74   $9.75   $9.70  
  7 purchase totals = $694.90       $733.8231   $733.83   $733.85   $733.70