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 $237.52   6.814%   $253.7046   $253.70   $253.70   $253.70  
  Purchase #2 $244.79   10.399%   $270.2457   $270.25   $270.25   $270.20  
  Purchase #3 $187.56   3.243%   $193.6426   $193.64   $193.65   $193.60  
  Purchase #4 $231.61   12.200%   $259.8664   $259.87   $259.85   $259.90  
  Purchase #5 $44.31   8.630%   $48.134   $48.13   $48.15   $48.10  
  Purchase #6 $185.60   4.767%   $194.4476   $194.45   $194.45   $194.40  
  Purchase #7 $169.25   4.539%   $176.9323   $176.93   $176.95   $176.90  
  7 purchase totals = $1,300.64       $1,396.9732   $1,396.97   $1,397.00   $1,396.80