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	$179.34	5.117%	$188.5168	$188.52	$188.50	$188.50
Purchase #2	$169.28	6.394%	$180.1038	$180.10	$180.10	$180.10
Purchase #3	$99.78	3.449%	$103.2214	$103.22	$103.20	$103.20
Purchase #4	$146.62	12.642%	$165.1557	$165.16	$165.15	$165.20
Purchase #5	$142.65	10.815%	$158.0776	$158.08	$158.10	$158.10
Purchase #6	$192.78	6.764%	$205.8196	$205.82	$205.80	$205.80
Purchase #7	$54.97	8.778%	$59.7953	$59.80	$59.80	$59.80
7 purchase totals =	$985.42		$1,060.6902	$1,060.70	$1,060.65	$1,060.70