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	$195.50	12.584%	$220.1017	$220.10	$220.10	$220.10
Purchase #2	$168.39	13.359%	$190.8852	$190.89	$190.90	$190.90
Purchase #3	$179.92	3.493%	$186.2046	$186.20	$186.20	$186.20
Purchase #4	$124.45	5.513%	$131.3109	$131.31	$131.30	$131.30
Purchase #5	$56.48	5.219%	$59.4277	$59.43	$59.45	$59.40
Purchase #6	$37.53	9.825%	$41.2173	$41.22	$41.20	$41.20
Purchase #7	$99.30	4.179%	$103.4497	$103.45	$103.45	$103.40
7 purchase totals =	$861.57		$932.5971	$932.60	$932.60	$932.50