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 $87.43   5.151%   $91.9335   $91.93   $91.95   $91.90  
  Purchase #2 $120.94   12.161%   $135.6475   $135.65   $135.65   $135.60  
  Purchase #3 $204.91   4.536%   $214.2047   $214.20   $214.20   $214.20  
  Purchase #4 $91.49   9.141%   $99.8531   $99.85   $99.85   $99.90  
  Purchase #5 $225.35   8.607%   $244.7459   $244.75   $244.75   $244.70  
  Purchase #6 $119.57   5.817%   $126.5254   $126.53   $126.55   $126.50  
  Purchase #7 $188.50   4.812%   $197.5706   $197.57   $197.55   $197.60  
  7 purchase totals = $1,038.19       $1,110.4807   $1,110.48   $1,110.50   $1,110.40