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 $182.98   6.792%   $195.408   $195.41   $195.40   $195.40  
  Purchase #2 $148.35   12.148%   $166.3716   $166.37   $166.35   $166.40  
  Purchase #3 $129.71   12.228%   $145.5709   $145.57   $145.55   $145.60  
  Purchase #4 $196.76   9.424%   $215.3027   $215.30   $215.30   $215.30  
  Purchase #5 $121.78   3.405%   $125.9266   $125.93   $125.95   $125.90  
  Purchase #6 $82.87   13.805%   $94.3102   $94.31   $94.30   $94.30  
  Purchase #7 $168.95   13.558%   $191.8562   $191.86   $191.85   $191.90  
  7 purchase totals = $1,031.40       $1,134.7462   $1,134.75   $1,134.70   $1,134.80