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 $70.36   7.673%   $75.7587   $75.76   $75.75   $75.80  
  Purchase #2 $218.55   12.517%   $245.9059   $245.91   $245.90   $245.90  
  Purchase #3 $202.60   13.756%   $230.4697   $230.47   $230.45   $230.50  
  Purchase #4 $239.44   10.660%   $264.9643   $264.96   $264.95   $265.00  
  Purchase #5 $204.72   7.780%   $220.6472   $220.65   $220.65   $220.60  
  Purchase #6 $28.70   12.679%   $32.3389   $32.34   $32.35   $32.30  
  Purchase #7 $84.37   8.386%   $91.4453   $91.45   $91.45   $91.40  
  7 purchase totals = $1,048.74       $1,161.5300   $1,161.54   $1,161.50   $1,161.50