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 $60.31   3.177%   $62.226   $62.23   $62.25   $62.20  
  Purchase #2 $226.34   3.397%   $234.0288   $234.03   $234.05   $234.00  
  Purchase #3 $152.57   5.301%   $160.6577   $160.66   $160.65   $160.70  
  Purchase #4 $20.98   6.329%   $22.3078   $22.31   $22.30   $22.30  
  Purchase #5 $65.38   3.113%   $67.4153   $67.42   $67.40   $67.40  
  Purchase #6 $13.80   11.268%   $15.355   $15.36   $15.35   $15.40  
  Purchase #7 $165.41   3.401%   $171.0356   $171.04   $171.05   $171.00  
  7 purchase totals = $704.79       $733.0262   $733.05   $733.05   $733.00