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 $191.54   9.452%   $209.6444   $209.64   $209.65   $209.60  
  Purchase #2 $241.86   9.147%   $263.9829   $263.98   $264.00   $264.00  
  Purchase #3 $71.79   7.265%   $77.0055   $77.01   $77.00   $77.00  
  Purchase #4 $175.33   12.639%   $197.49   $197.49   $197.50   $197.50  
  Purchase #5 $68.74   12.470%   $77.3119   $77.31   $77.30   $77.30  
  Purchase #6 $196.74   4.347%   $205.2923   $205.29   $205.30   $205.30  
  Purchase #7 $91.56   3.690%   $94.9386   $94.94   $94.95   $94.90  
  7 purchase totals = $1,037.56       $1,125.6656   $1,125.66   $1,125.70   $1,125.60