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 $181.40   7.672%   $195.317   $195.32   $195.30   $195.30  
  Purchase #2 $219.31   8.572%   $238.1093   $238.11   $238.10   $238.10  
  Purchase #3 $219.45   8.192%   $237.4273   $237.43   $237.45   $237.40  
  Purchase #4 $88.99   8.825%   $96.8434   $96.84   $96.85   $96.80  
  Purchase #5 $171.46   5.585%   $181.036   $181.04   $181.05   $181.00  
  Purchase #6 $23.53   5.709%   $24.8733   $24.87   $24.85   $24.90  
  Purchase #7 $37.70   7.721%   $40.6108   $40.61   $40.60   $40.60  
  7 purchase totals = $941.84       $1,014.2171   $1,014.22   $1,014.20   $1,014.10