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 $56.82   10.761%   $62.9344   $62.93   $62.95   $62.90  
  Purchase #2 $243.85   13.261%   $276.1869   $276.19   $276.20   $276.20  
  Purchase #3 $184.62   9.548%   $202.2475   $202.25   $202.25   $202.20  
  Purchase #4 $86.27   5.360%   $90.8941   $90.89   $90.90   $90.90  
  Purchase #5 $6.29   9.294%   $6.8746   $6.87   $6.85   $6.90  
  Purchase #6 $241.62   8.656%   $262.5346   $262.53   $262.55   $262.50  
  Purchase #7 $176.44   7.423%   $189.5371   $189.54   $189.55   $189.50  
  7 purchase totals = $995.91       $1,091.2092   $1,091.20   $1,091.25   $1,091.10