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	$145.42	6.847%	$155.3769	$155.38	$155.40	$155.40
Purchase #2	$173.35	12.679%	$195.329	$195.33	$195.35	$195.30
Purchase #3	$94.69	4.762%	$99.1991	$99.20	$99.20	$99.20
Purchase #4	$154.57	4.109%	$160.9213	$160.92	$160.90	$160.90
Purchase #5	$175.35	12.854%	$197.8895	$197.89	$197.90	$197.90
Purchase #6	$100.75	4.516%	$105.2999	$105.30	$105.30	$105.30
Purchase #7	$189.84	3.469%	$196.4255	$196.43	$196.45	$196.40
7 purchase totals =	$1,033.97		$1,110.4412	$1,110.45	$1,110.50	$1,110.40