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	$32.44	6.426%	$34.5246	$34.52	$34.50	$34.50
Purchase #2	$176.62	10.670%	$195.4654	$195.47	$195.45	$195.50
Purchase #3	$191.64	12.333%	$215.275	$215.28	$215.30	$215.30
Purchase #4	$73.45	13.431%	$83.3151	$83.32	$83.30	$83.30
Purchase #5	$245.71	5.309%	$258.7547	$258.75	$258.75	$258.80
Purchase #6	$20.43	11.522%	$22.7839	$22.78	$22.80	$22.80
Purchase #7	$223.65	4.332%	$233.3385	$233.34	$233.35	$233.30
7 purchase totals =	$963.94		$1,043.4572	$1,043.46	$1,043.45	$1,043.50