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 $103.52   13.694%   $117.696   $117.70   $117.70   $117.70  
  Purchase #2 $148.55   3.128%   $153.1966   $153.20   $153.20   $153.20  
  Purchase #3 $191.98   4.730%   $201.0607   $201.06   $201.05   $201.10  
  Purchase #4 $76.95   9.245%   $84.064   $84.06   $84.05   $84.10  
  Purchase #5 $89.48   4.272%   $93.3026   $93.30   $93.30   $93.30  
  Purchase #6 $158.58   12.414%   $178.2661   $178.27   $178.25   $178.30  
  Purchase #7 $237.89   12.631%   $267.9379   $267.94   $267.95   $267.90  
  7 purchase totals = $1,006.95       $1,095.5239   $1,095.53   $1,095.50   $1,095.60