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 $49.26   5.567%   $52.0023   $52.00   $52.00   $52.00  
  Purchase #2 $232.25   5.818%   $245.7623   $245.76   $245.75   $245.80  
  Purchase #3 $243.27   5.415%   $256.4431   $256.44   $256.45   $256.40  
  Purchase #4 $206.99   6.213%   $219.8503   $219.85   $219.85   $219.90  
  Purchase #5 $197.44   12.217%   $221.5612   $221.56   $221.55   $221.60  
  Purchase #6 $147.34   4.171%   $153.4856   $153.49   $153.50   $153.50  
  Purchase #7 $140.59   12.681%   $158.4182   $158.42   $158.40   $158.40  
  7 purchase totals = $1,217.14       $1,307.5230   $1,307.52   $1,307.50   $1,307.60