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	$247.42	13.791%	$281.5417	$281.54	$281.55	$281.50
Purchase #2	$46.72	8.835%	$50.8477	$50.85	$50.85	$50.80
Purchase #3	$52.70	13.111%	$59.6095	$59.61	$59.60	$59.60
Purchase #4	$173.66	6.614%	$185.1459	$185.15	$185.15	$185.10
Purchase #5	$202.55	7.258%	$217.2511	$217.25	$217.25	$217.30
Purchase #6	$97.88	11.528%	$109.1636	$109.16	$109.15	$109.20
Purchase #7	$241.92	4.854%	$253.6628	$253.66	$253.65	$253.70
7 purchase totals =	$1,062.85		$1,157.2223	$1,157.22	$1,157.20	$1,157.20