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 $103.53   10.126%   $114.0134   $114.01   $114.00   $114.00  
  Purchase #2 $83.96   9.556%   $91.9832   $91.98   $92.00   $92.00  
  Purchase #3 $175.96   12.648%   $198.2154   $198.22   $198.20   $198.20  
  Purchase #4 $199.86   6.368%   $212.5871   $212.59   $212.60   $212.60  
  Purchase #5 $145.46   4.738%   $152.3519   $152.35   $152.35   $152.40  
  Purchase #6 $199.78   9.193%   $218.1458   $218.15   $218.15   $218.10  
  Purchase #7 $17.64   5.864%   $18.6744   $18.67   $18.65   $18.70  
  7 purchase totals = $926.19       $1,005.9712   $1,005.97   $1,005.95   $1,006.00