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	$175.38	9.300%	$191.6903	$191.69	$191.70	$191.70
Purchase #2	$166.72	11.169%	$185.341	$185.34	$185.35	$185.30
Purchase #3	$233.66	5.722%	$247.03	$247.03	$247.05	$247.00
Purchase #4	$122.56	11.707%	$136.9081	$136.91	$136.90	$136.90
Purchase #5	$238.32	10.296%	$262.8574	$262.86	$262.85	$262.90
Purchase #6	$33.28	3.286%	$34.3736	$34.37	$34.35	$34.40
Purchase #7	$161.77	3.457%	$167.3624	$167.36	$167.35	$167.40
7 purchase totals =	$1,131.69		$1,225.5628	$1,225.56	$1,225.55	$1,225.60