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 $58.64   6.296%   $62.332   $62.33   $62.35   $62.30  
  Purchase #2 $217.67   7.810%   $234.67   $234.67   $234.65   $234.70  
  Purchase #3 $128.29   5.580%   $135.4486   $135.45   $135.45   $135.40  
  Purchase #4 $51.39   9.642%   $56.345   $56.35   $56.35   $56.30  
  Purchase #5 $230.42   6.521%   $245.4457   $245.45   $245.45   $245.40  
  Purchase #6 $104.53   10.370%   $115.3698   $115.37   $115.35   $115.40  
  Purchase #7 $135.30   13.166%   $153.1136   $153.11   $153.10   $153.10  
  7 purchase totals = $926.24       $1,002.7247   $1,002.73   $1,002.70   $1,002.60