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	$106.77	10.519%	$118.0011	$118.00	$118.00	$118.00
Purchase #2	$55.70	10.339%	$61.4588	$61.46	$61.45	$61.50
Purchase #3	$202.65	6.175%	$215.1636	$215.16	$215.15	$215.20
Purchase #4	$133.90	13.160%	$151.5212	$151.52	$151.50	$151.50
Purchase #5	$147.66	7.490%	$158.7197	$158.72	$158.70	$158.70
Purchase #6	$165.26	13.745%	$187.975	$187.98	$188.00	$188.00
Purchase #7	$89.56	4.541%	$93.6269	$93.63	$93.65	$93.60
7 purchase totals =	$901.50		$986.4663	$986.47	$986.45	$986.50