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 $62.60   3.701%   $64.9168   $64.92   $64.90   $64.90  
  Purchase #2 $232.53   4.193%   $242.28   $242.28   $242.30   $242.30  
  Purchase #3 $88.72   7.396%   $95.2817   $95.28   $95.30   $95.30  
  Purchase #4 $159.77   11.189%   $177.6467   $177.65   $177.65   $177.60  
  Purchase #5 $77.67   11.207%   $86.3745   $86.37   $86.35   $86.40  
  Purchase #6 $170.95   10.727%   $189.2878   $189.29   $189.30   $189.30  
  Purchase #7 $214.53   6.802%   $229.1223   $229.12   $229.10   $229.10  
  7 purchase totals = $1,006.77       $1,084.9098   $1,084.91   $1,084.90   $1,084.90