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	$35.65	4.819%	$37.368	$37.37	$37.35	$37.40
Purchase #2	$174.52	3.759%	$181.0802	$181.08	$181.10	$181.10
Purchase #3	$239.55	8.683%	$260.3501	$260.35	$260.35	$260.40
Purchase #4	$50.64	5.281%	$53.3143	$53.31	$53.30	$53.30
Purchase #5	$167.33	5.488%	$176.5131	$176.51	$176.50	$176.50
Purchase #6	$123.33	13.201%	$139.6108	$139.61	$139.60	$139.60
Purchase #7	$221.31	11.698%	$247.1988	$247.20	$247.20	$247.20
7 purchase totals =	$1,012.33		$1,095.4353	$1,095.43	$1,095.40	$1,095.50