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	$94.58	3.154%	$97.5631	$97.56	$97.55	$97.60
Purchase #2	$59.29	13.504%	$67.2965	$67.30	$67.30	$67.30
Purchase #3	$151.50	10.532%	$167.456	$167.46	$167.45	$167.50
Purchase #4	$99.42	10.184%	$109.5449	$109.54	$109.55	$109.50
Purchase #5	$114.34	11.867%	$127.9087	$127.91	$127.90	$127.90
Purchase #6	$30.59	4.823%	$32.0654	$32.07	$32.05	$32.10
Purchase #7	$236.25	3.475%	$244.4597	$244.46	$244.45	$244.50
7 purchase totals =	$785.97		$846.2943	$846.30	$846.25	$846.40