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 $243.57   7.679%   $262.2737   $262.27   $262.25   $262.30  
  Purchase #2 $88.51   8.432%   $95.9732   $95.97   $95.95   $96.00  
  Purchase #3 $207.60   13.108%   $234.8122   $234.81   $234.80   $234.80  
  Purchase #4 $128.82   3.588%   $133.4421   $133.44   $133.45   $133.40  
  Purchase #5 $204.84   7.352%   $219.8998   $219.90   $219.90   $219.90  
  Purchase #6 $106.35   6.264%   $113.0118   $113.01   $113.00   $113.00  
  Purchase #7 $96.54   8.631%   $104.8724   $104.87   $104.85   $104.90  
  7 purchase totals = $1,076.23       $1,164.2852   $1,164.27   $1,164.20   $1,164.30