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 $194.74   5.232%   $204.9288   $204.93   $204.95   $204.90  
  Purchase #2 $219.39   11.466%   $244.5453   $244.55   $244.55   $244.50  
  Purchase #3 $32.41   3.483%   $33.5388   $33.54   $33.55   $33.50  
  Purchase #4 $136.80   12.172%   $153.4513   $153.45   $153.45   $153.50  
  Purchase #5 $110.73   5.330%   $116.6319   $116.63   $116.65   $116.60  
  Purchase #6 $209.81   11.638%   $234.2277   $234.23   $234.25   $234.20  
  Purchase #7 $175.37   3.562%   $181.6167   $181.62   $181.60   $181.60  
  7 purchase totals = $1,079.25       $1,168.9405   $1,168.95   $1,169.00   $1,168.80