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 $126.56   12.213%   $142.0168   $142.02   $142.00   $142.00  
  Purchase #2 $244.73   6.279%   $260.0966   $260.10   $260.10   $260.10  
  Purchase #3 $34.25   6.535%   $36.4882   $36.49   $36.50   $36.50  
  Purchase #4 $198.53   11.694%   $221.7461   $221.75   $221.75   $221.70  
  Purchase #5 $84.85   4.422%   $88.6021   $88.60   $88.60   $88.60  
  Purchase #6 $116.51   4.252%   $121.464   $121.46   $121.45   $121.50  
  Purchase #7 $143.87   6.194%   $152.7813   $152.78   $152.80   $152.80  
  7 purchase totals = $949.30       $1,023.1951   $1,023.20   $1,023.20   $1,023.20