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	$160.98	8.481%	$174.6327	$174.63	$174.65	$174.60
Purchase #2	$158.93	4.311%	$165.7815	$165.78	$165.80	$165.80
Purchase #3	$40.92	10.868%	$45.3672	$45.37	$45.35	$45.40
Purchase #4	$230.33	12.735%	$259.6625	$259.66	$259.65	$259.70
Purchase #5	$40.68	4.252%	$42.4097	$42.41	$42.40	$42.40
Purchase #6	$228.91	5.332%	$241.1155	$241.12	$241.10	$241.10
Purchase #7	$80.40	11.336%	$89.5141	$89.51	$89.50	$89.50
7 purchase totals =	$941.15		$1,018.4832	$1,018.48	$1,018.45	$1,018.50