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	$155.47	3.463%	$160.8539	$160.85	$160.85	$160.90
Purchase #2	$64.66	11.810%	$72.2963	$72.30	$72.30	$72.30
Purchase #3	$221.68	8.414%	$240.3322	$240.33	$240.35	$240.30
Purchase #4	$47.61	12.462%	$53.5432	$53.54	$53.55	$53.50
Purchase #5	$234.86	6.579%	$250.3114	$250.31	$250.30	$250.30
Purchase #6	$228.93	13.120%	$258.9656	$258.97	$258.95	$259.00
Purchase #7	$144.31	3.323%	$149.1054	$149.11	$149.10	$149.10
7 purchase totals =	$1,097.52		$1,185.4080	$1,185.41	$1,185.40	$1,185.40