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 $211.86   10.266%   $233.6095   $233.61   $233.60   $233.60  
  Purchase #2 $203.40   7.683%   $219.0272   $219.03   $219.05   $219.00  
  Purchase #3 $197.97   7.445%   $212.7089   $212.71   $212.70   $212.70  
  Purchase #4 $56.73   4.250%   $59.141   $59.14   $59.15   $59.10  
  Purchase #5 $64.82   3.323%   $66.974   $66.97   $66.95   $67.00  
  Purchase #6 $97.85   9.556%   $107.2005   $107.20   $107.20   $107.20  
  Purchase #7 $200.55   12.506%   $225.6308   $225.63   $225.65   $225.60  
  7 purchase totals = $1,033.18       $1,124.2919   $1,124.29   $1,124.30   $1,124.20