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 $88.94   7.339%   $95.4673   $95.47   $95.45   $95.50  
  Purchase #2 $201.88   12.165%   $226.4387   $226.44   $226.45   $226.40  
  Purchase #3 $187.34   13.344%   $212.3386   $212.34   $212.35   $212.30  
  Purchase #4 $124.58   9.840%   $136.8387   $136.84   $136.85   $136.80  
  Purchase #5 $247.27   5.488%   $260.8402   $260.84   $260.85   $260.80  
  Purchase #6 $154.67   11.541%   $172.5205   $172.52   $172.50   $172.50  
  Purchase #7 $13.26   4.641%   $13.8754   $13.88   $13.90   $13.90  
  7 purchase totals = $1,017.94       $1,118.3194   $1,118.33   $1,118.35   $1,118.20