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 $216.68   11.353%   $241.2797   $241.28   $241.30   $241.30  
  Purchase #2 $10.32   12.293%   $11.5886   $11.59   $11.60   $11.60  
  Purchase #3 $11.28   11.806%   $12.6117   $12.61   $12.60   $12.60  
  Purchase #4 $102.67   10.222%   $113.1649   $113.16   $113.15   $113.20  
  Purchase #5 $216.82   12.620%   $244.1827   $244.18   $244.20   $244.20  
  Purchase #6 $228.80   7.596%   $246.1796   $246.18   $246.20   $246.20  
  Purchase #7 $237.68   3.445%   $245.8681   $245.87   $245.85   $245.90  
  7 purchase totals = $1,024.25       $1,114.8753   $1,114.87   $1,114.90   $1,115.00