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 $92.43   3.546%   $95.7076   $95.71   $95.70   $95.70  
  Purchase #2 $85.46   11.245%   $95.07   $95.07   $95.05   $95.10  
  Purchase #3 $50.61   3.166%   $52.2123   $52.21   $52.20   $52.20  
  Purchase #4 $118.77   9.522%   $130.0793   $130.08   $130.10   $130.10  
  Purchase #5 $184.68   11.364%   $205.667   $205.67   $205.65   $205.70  
  Purchase #6 $221.75   7.121%   $237.5408   $237.54   $237.55   $237.50  
  Purchase #7 $75.27   8.196%   $81.4391   $81.44   $81.45   $81.40  
  7 purchase totals = $828.97       $897.7161   $897.72   $897.70   $897.70