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 $183.26   10.743%   $202.9476   $202.95   $202.95   $202.90  
  Purchase #2 $15.44   7.244%   $16.5585   $16.56   $16.55   $16.60  
  Purchase #3 $120.64   6.287%   $128.2246   $128.22   $128.20   $128.20  
  Purchase #4 $163.92   8.843%   $178.4154   $178.42   $178.40   $178.40  
  Purchase #5 $219.38   3.453%   $226.9552   $226.96   $226.95   $227.00  
  Purchase #6 $203.67   6.119%   $216.1326   $216.13   $216.15   $216.10  
  Purchase #7 $90.47   4.532%   $94.5701   $94.57   $94.55   $94.60  
  7 purchase totals = $996.78       $1,063.8040   $1,063.81   $1,063.75   $1,063.80