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 $243.96   7.107%   $261.2982   $261.30   $261.30   $261.30  
  Purchase #2 $203.51   6.271%   $216.2721   $216.27   $216.25   $216.30  
  Purchase #3 $145.52   4.457%   $152.0058   $152.01   $152.00   $152.00  
  Purchase #4 $57.94   7.780%   $62.4477   $62.45   $62.45   $62.40  
  Purchase #5 $127.84   3.546%   $132.3732   $132.37   $132.35   $132.40  
  Purchase #6 $211.29   4.434%   $220.6586   $220.66   $220.65   $220.70  
  Purchase #7 $197.60   8.651%   $214.6944   $214.69   $214.70   $214.70  
  7 purchase totals = $1,187.66       $1,259.7500   $1,259.75   $1,259.70   $1,259.80