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 $92.44   3.506%   $95.6809   $95.68   $95.70   $95.70  
  Purchase #2 $159.78   9.293%   $174.6284   $174.63   $174.65   $174.60  
  Purchase #3 $147.42   12.591%   $165.9817   $165.98   $166.00   $166.00  
  Purchase #4 $41.73   10.180%   $45.9781   $45.98   $46.00   $46.00  
  Purchase #5 $85.28   10.444%   $94.1866   $94.19   $94.20   $94.20  
  Purchase #6 $89.94   10.580%   $99.4557   $99.46   $99.45   $99.50  
  Purchase #7 $18.52   6.263%   $19.6799   $19.68   $19.70   $19.70  
  7 purchase totals = $635.11       $695.5913   $695.60   $695.70   $695.70