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	$241.98	5.297%	$254.7977	$254.80	$254.80	$254.80
Purchase #2	$95.64	9.180%	$104.4198	$104.42	$104.40	$104.40
Purchase #3	$17.77	13.187%	$20.1133	$20.11	$20.10	$20.10
Purchase #4	$149.79	10.263%	$165.1629	$165.16	$165.15	$165.20
Purchase #5	$64.88	11.255%	$72.1822	$72.18	$72.20	$72.20
Purchase #6	$201.39	4.577%	$210.6076	$210.61	$210.60	$210.60
Purchase #7	$250.80	10.112%	$276.1609	$276.16	$276.15	$276.20
7 purchase totals =	$1,022.25		$1,103.4444	$1,103.44	$1,103.40	$1,103.50