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	$39.34	4.259%	$41.0155	$41.02	$41.00	$41.00
Purchase #2	$81.93	10.382%	$90.436	$90.44	$90.45	$90.40
Purchase #3	$69.88	3.180%	$72.1022	$72.10	$72.10	$72.10
Purchase #4	$165.74	4.150%	$172.6182	$172.62	$172.60	$172.60
Purchase #5	$188.27	3.141%	$194.1836	$194.18	$194.20	$194.20
Purchase #6	$100.30	13.397%	$113.7372	$113.74	$113.75	$113.70
Purchase #7	$29.31	4.281%	$30.5648	$30.56	$30.55	$30.60
7 purchase totals =	$674.77		$714.6575	$714.66	$714.65	$714.60