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	$244.25	12.339%	$274.388	$274.39	$274.40	$274.40
Purchase #2	$35.57	13.590%	$40.404	$40.40	$40.40	$40.40
Purchase #3	$60.79	11.286%	$67.6508	$67.65	$67.65	$67.70
Purchase #4	$58.87	5.485%	$62.099	$62.10	$62.10	$62.10
Purchase #5	$80.61	5.511%	$85.0524	$85.05	$85.05	$85.10
Purchase #6	$204.28	3.695%	$211.8281	$211.83	$211.85	$211.80
Purchase #7	$22.51	10.619%	$24.9003	$24.90	$24.90	$24.90
7 purchase totals =	$706.88		$766.3226	$766.32	$766.35	$766.40