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 $58.40   7.636%   $62.8594   $62.86   $62.85   $62.90  
  Purchase #2 $215.34   4.582%   $225.2069   $225.21   $225.20   $225.20  
  Purchase #3 $101.41   9.207%   $110.7468   $110.75   $110.75   $110.70  
  Purchase #4 $195.34   11.674%   $218.144   $218.14   $218.15   $218.10  
  Purchase #5 $217.51   5.163%   $228.74   $228.74   $228.75   $228.70  
  Purchase #6 $98.65   5.651%   $104.2247   $104.22   $104.20   $104.20  
  Purchase #7 $237.41   13.635%   $269.7809   $269.78   $269.80   $269.80  
  7 purchase totals = $1,124.06       $1,219.7027   $1,219.70   $1,219.70   $1,219.60