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	$226.66	6.283%	$240.901	$240.90	$240.90	$240.90
Purchase #2	$149.81	7.671%	$161.3019	$161.30	$161.30	$161.30
Purchase #3	$186.31	5.451%	$196.4658	$196.47	$196.45	$196.50
Purchase #4	$71.46	4.227%	$74.4806	$74.48	$74.50	$74.50
Purchase #5	$80.60	6.451%	$85.7995	$85.80	$85.80	$85.80
Purchase #6	$197.76	6.469%	$210.5531	$210.55	$210.55	$210.60
Purchase #7	$118.90	7.558%	$127.8865	$127.89	$127.90	$127.90
7 purchase totals =	$1,031.50		$1,097.3884	$1,097.39	$1,097.40	$1,097.50