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 $44.44   8.794%   $48.3481   $48.35   $48.35   $48.30  
  Purchase #2 $156.69   12.110%   $175.6652   $175.67   $175.65   $175.70  
  Purchase #3 $200.39   6.721%   $213.8582   $213.86   $213.85   $213.90  
  Purchase #4 $178.45   3.495%   $184.6868   $184.69   $184.70   $184.70  
  Purchase #5 $6.98   11.477%   $7.7811   $7.78   $7.80   $7.80  
  Purchase #6 $86.65   10.753%   $95.9675   $95.97   $95.95   $96.00  
  Purchase #7 $161.28   10.520%   $178.2467   $178.25   $178.25   $178.20  
  7 purchase totals = $834.88       $904.5536   $904.57   $904.55   $904.60