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 $87.96   8.311%   $95.2704   $95.27   $95.25   $95.30  
  Purchase #2 $168.33   9.627%   $184.5351   $184.54   $184.55   $184.50  
  Purchase #3 $194.61   10.117%   $214.2987   $214.30   $214.30   $214.30  
  Purchase #4 $210.97   6.777%   $225.2674   $225.27   $225.25   $225.30  
  Purchase #5 $54.65   10.221%   $60.2358   $60.24   $60.25   $60.20  
  Purchase #6 $104.39   4.294%   $108.8725   $108.87   $108.85   $108.90  
  Purchase #7 $218.28   11.633%   $243.6725   $243.67   $243.65   $243.70  
  7 purchase totals = $1,039.19       $1,132.1524   $1,132.16   $1,132.10   $1,132.20