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	$136.83	12.131%	$153.4288	$153.43	$153.45	$153.40
Purchase #2	$158.77	10.261%	$175.0614	$175.06	$175.05	$175.10
Purchase #3	$55.85	12.488%	$62.8245	$62.82	$62.80	$62.80
Purchase #4	$219.94	4.598%	$230.0528	$230.05	$230.05	$230.10
Purchase #5	$73.96	13.337%	$83.824	$83.82	$83.80	$83.80
Purchase #6	$160.95	3.816%	$167.0919	$167.09	$167.10	$167.10
Purchase #7	$176.56	11.132%	$196.2147	$196.21	$196.20	$196.20
7 purchase totals =	$982.86		$1,068.4981	$1,068.48	$1,068.45	$1,068.50