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 $43.50   8.302%   $47.1114   $47.11   $47.10   $47.10  
  Purchase #2 $209.74   4.727%   $219.6544   $219.65   $219.65   $219.70  
  Purchase #3 $39.41   5.844%   $41.7131   $41.71   $41.70   $41.70  
  Purchase #4 $216.62   6.356%   $230.3884   $230.39   $230.40   $230.40  
  Purchase #5 $236.96   9.714%   $259.9783   $259.98   $260.00   $260.00  
  Purchase #6 $219.49   9.417%   $240.1594   $240.16   $240.15   $240.20  
  Purchase #7 $14.36   3.368%   $14.8436   $14.84   $14.85   $14.80  
  7 purchase totals = $980.08       $1,053.8486   $1,053.84   $1,053.85   $1,053.90