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 $93.28   3.200%   $96.265   $96.27   $96.25   $96.30  
  Purchase #2 $80.32   6.694%   $85.6966   $85.70   $85.70   $85.70  
  Purchase #3 $53.85   6.140%   $57.1564   $57.16   $57.15   $57.20  
  Purchase #4 $195.47   8.328%   $211.7487   $211.75   $211.75   $211.70  
  Purchase #5 $171.64   9.325%   $187.6454   $187.65   $187.65   $187.60  
  Purchase #6 $100.90   7.360%   $108.3262   $108.33   $108.35   $108.30  
  Purchase #7 $40.43   13.838%   $46.0247   $46.02   $46.00   $46.00  
  7 purchase totals = $735.89       $792.8630   $792.88   $792.85   $792.80