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	$240.40	10.188%	$264.892	$264.89	$264.90	$264.90
Purchase #2	$183.61	7.377%	$197.1549	$197.15	$197.15	$197.20
Purchase #3	$187.75	4.748%	$196.6644	$196.66	$196.65	$196.70
Purchase #4	$240.94	9.206%	$263.1209	$263.12	$263.10	$263.10
Purchase #5	$32.27	7.469%	$34.6802	$34.68	$34.70	$34.70
Purchase #6	$155.55	11.106%	$172.8254	$172.83	$172.85	$172.80
Purchase #7	$223.52	3.730%	$231.8573	$231.86	$231.85	$231.90
7 purchase totals =	$1,264.04		$1,361.1951	$1,361.19	$1,361.20	$1,361.30