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 $181.26   5.758%   $191.697   $191.70   $191.70   $191.70  
  Purchase #2 $37.70   5.711%   $39.853   $39.85   $39.85   $39.90  
  Purchase #3 $231.89   9.161%   $253.1334   $253.13   $253.15   $253.10  
  Purchase #4 $73.94   8.491%   $80.2182   $80.22   $80.20   $80.20  
  Purchase #5 $184.93   3.220%   $190.8847   $190.88   $190.90   $190.90  
  Purchase #6 $22.56   7.555%   $24.2644   $24.26   $24.25   $24.30  
  Purchase #7 $41.29   9.522%   $45.2216   $45.22   $45.20   $45.20  
  7 purchase totals = $773.57       $825.2723   $825.26   $825.25   $825.30