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 $92.61   12.246%   $103.951   $103.95   $103.95   $104.00  
  Purchase #2 $170.90   12.306%   $191.931   $191.93   $191.95   $191.90  
  Purchase #3 $86.71   8.180%   $93.8029   $93.80   $93.80   $93.80  
  Purchase #4 $60.31   4.671%   $63.1271   $63.13   $63.15   $63.10  
  Purchase #5 $153.25   5.167%   $161.1684   $161.17   $161.15   $161.20  
  Purchase #6 $185.65   8.848%   $202.0763   $202.08   $202.10   $202.10  
  Purchase #7 $56.45   7.325%   $60.585   $60.59   $60.60   $60.60  
  7 purchase totals = $805.88       $876.6417   $876.65   $876.70   $876.70