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 $41.35   8.185%   $44.7345   $44.73   $44.75   $44.70  
  Purchase #2 $212.44   13.816%   $241.7907   $241.79   $241.80   $241.80  
  Purchase #3 $68.53   8.451%   $74.3215   $74.32   $74.30   $74.30  
  Purchase #4 $119.54   7.108%   $128.0369   $128.04   $128.05   $128.00  
  Purchase #5 $166.28   7.610%   $178.9339   $178.93   $178.95   $178.90  
  Purchase #6 $231.96   9.698%   $254.4555   $254.46   $254.45   $254.50  
  Purchase #7 $158.75   8.332%   $171.9771   $171.98   $172.00   $172.00  
  7 purchase totals = $998.85       $1,094.2501   $1,094.25   $1,094.30   $1,094.20