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 $96.73   7.821%   $104.2953   $104.30   $104.30   $104.30  
  Purchase #2 $130.54   7.762%   $140.6725   $140.67   $140.65   $140.70  
  Purchase #3 $204.56   7.135%   $219.1554   $219.16   $219.15   $219.20  
  Purchase #4 $216.45   13.743%   $246.1967   $246.20   $246.20   $246.20  
  Purchase #5 $217.74   13.615%   $247.3853   $247.39   $247.40   $247.40  
  Purchase #6 $220.64   8.363%   $239.0921   $239.09   $239.10   $239.10  
  Purchase #7 $234.60   4.339%   $244.7793   $244.78   $244.80   $244.80  
  7 purchase totals = $1,321.26       $1,441.5766   $1,441.59   $1,441.60   $1,441.70