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 $51.48   13.459%   $58.4087   $58.41   $58.40   $58.40  
  Purchase #2 $142.27   6.677%   $151.7694   $151.77   $151.75   $151.80  
  Purchase #3 $30.75   9.500%   $33.6713   $33.67   $33.65   $33.70  
  Purchase #4 $197.72   6.808%   $211.1808   $211.18   $211.20   $211.20  
  Purchase #5 $160.36   13.176%   $181.489   $181.49   $181.50   $181.50  
  Purchase #6 $204.86   6.229%   $217.6207   $217.62   $217.60   $217.60  
  Purchase #7 $233.42   3.282%   $241.0808   $241.08   $241.10   $241.10  
  7 purchase totals = $1,020.86       $1,095.2207   $1,095.22   $1,095.20   $1,095.30