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 $83.62   13.583%   $94.9781   $94.98   $95.00   $95.00  
  Purchase #2 $67.77   11.572%   $75.6123   $75.61   $75.60   $75.60  
  Purchase #3 $157.33   7.292%   $168.8025   $168.80   $168.80   $168.80  
  Purchase #4 $240.53   5.213%   $253.0688   $253.07   $253.05   $253.10  
  Purchase #5 $128.31   8.297%   $138.9559   $138.96   $138.95   $139.00  
  Purchase #6 $113.80   9.529%   $124.644   $124.64   $124.65   $124.60  
  Purchase #7 $213.28   5.395%   $224.7865   $224.79   $224.80   $224.80  
  7 purchase totals = $1,004.64       $1,080.8481   $1,080.85   $1,080.85   $1,080.90