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 $246.53   7.512%   $265.0493   $265.05   $265.05   $265.00  
  Purchase #2 $31.59   6.718%   $33.7122   $33.71   $33.70   $33.70  
  Purchase #3 $219.30   11.856%   $245.3002   $245.30   $245.30   $245.30  
  Purchase #4 $62.39   9.292%   $68.1873   $68.19   $68.20   $68.20  
  Purchase #5 $205.59   5.858%   $217.6335   $217.63   $217.65   $217.60  
  Purchase #6 $14.85   9.137%   $16.2068   $16.21   $16.20   $16.20  
  Purchase #7 $191.44   6.601%   $204.077   $204.08   $204.10   $204.10  
  7 purchase totals = $971.69       $1,050.1663   $1,050.17   $1,050.20   $1,050.10