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 $195.83   8.274%   $212.033   $212.03   $212.05   $212.00  
  Purchase #2 $13.29   9.245%   $14.5187   $14.52   $14.50   $14.50  
  Purchase #3 $93.41   6.826%   $99.7862   $99.79   $99.80   $99.80  
  Purchase #4 $60.62   12.595%   $68.2551   $68.26   $68.25   $68.30  
  Purchase #5 $193.38   9.102%   $210.9814   $210.98   $211.00   $211.00  
  Purchase #6 $110.61   5.231%   $116.396   $116.40   $116.40   $116.40  
  Purchase #7 $164.95   4.556%   $172.4651   $172.47   $172.45   $172.50  
  7 purchase totals = $832.09       $894.4355   $894.45   $894.45   $894.50