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	$40.94	13.255%	$46.3666	$46.37	$46.35	$46.40
Purchase #2	$57.95	8.552%	$62.9059	$62.91	$62.90	$62.90
Purchase #3	$239.69	13.349%	$271.6862	$271.69	$271.70	$271.70
Purchase #4	$150.45	11.385%	$167.5787	$167.58	$167.60	$167.60
Purchase #5	$218.75	3.371%	$226.1241	$226.12	$226.10	$226.10
Purchase #6	$127.45	7.324%	$136.7844	$136.78	$136.80	$136.80
Purchase #7	$99.98	11.369%	$111.3467	$111.35	$111.35	$111.30
7 purchase totals =	$935.21		$1,022.7926	$1,022.80	$1,022.80	$1,022.80