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 $44.70   4.706%   $46.8036   $46.80   $46.80   $46.80  
  Purchase #2 $55.84   7.435%   $59.9917   $59.99   $60.00   $60.00  
  Purchase #3 $31.91   5.158%   $33.5559   $33.56   $33.55   $33.60  
  Purchase #4 $196.37   7.327%   $210.758   $210.76   $210.75   $210.80  
  Purchase #5 $227.29   9.565%   $249.0303   $249.03   $249.05   $249.00  
  Purchase #6 $236.92   9.726%   $259.9628   $259.96   $259.95   $260.00  
  Purchase #7 $189.58   7.140%   $203.116   $203.12   $203.10   $203.10  
  7 purchase totals = $982.61       $1,063.2183   $1,063.22   $1,063.20   $1,063.30