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 $44.31   8.700%   $48.165   $48.17   $48.15   $48.20  
  Purchase #2 $169.85   8.712%   $184.6473   $184.65   $184.65   $184.60  
  Purchase #3 $104.96   5.112%   $110.3256   $110.33   $110.35   $110.30  
  Purchase #4 $48.58   10.350%   $53.608   $53.61   $53.60   $53.60  
  Purchase #5 $212.93   4.391%   $222.2798   $222.28   $222.30   $222.30  
  Purchase #6 $197.73   8.467%   $214.4718   $214.47   $214.45   $214.50  
  Purchase #7 $195.47   3.548%   $202.4053   $202.41   $202.40   $202.40  
  7 purchase totals = $973.83       $1,035.9028   $1,035.92   $1,035.90   $1,035.90