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	$158.59	4.574%	$165.8439	$165.84	$165.85	$165.80
Purchase #2	$164.57	12.672%	$185.4243	$185.42	$185.40	$185.40
Purchase #3	$80.71	13.422%	$91.5429	$91.54	$91.55	$91.50
Purchase #4	$92.26	4.504%	$96.4154	$96.42	$96.40	$96.40
Purchase #5	$127.51	5.696%	$134.773	$134.77	$134.75	$134.80
Purchase #6	$114.82	4.296%	$119.7527	$119.75	$119.75	$119.80
Purchase #7	$142.59	11.633%	$159.1775	$159.18	$159.20	$159.20
7 purchase totals =	$881.05		$952.9297	$952.92	$952.90	$952.90