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 $180.48   8.597%   $195.9959   $196.00   $196.00   $196.00  
  Purchase #2 $164.95   5.210%   $173.5439   $173.54   $173.55   $173.50  
  Purchase #3 $205.91   6.333%   $218.9503   $218.95   $218.95   $219.00  
  Purchase #4 $43.84   12.491%   $49.3161   $49.32   $49.30   $49.30  
  Purchase #5 $203.68   4.204%   $212.2427   $212.24   $212.25   $212.20  
  Purchase #6 $31.93   5.411%   $33.6577   $33.66   $33.65   $33.70  
  Purchase #7 $172.88   6.599%   $184.2884   $184.29   $184.30   $184.30  
  7 purchase totals = $1,003.67       $1,067.9950   $1,068.00   $1,068.00   $1,068.00