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	$110.85	11.712%	$123.8328	$123.83	$123.85	$123.80
Purchase #2	$229.83	6.158%	$243.9829	$243.98	$244.00	$244.00
Purchase #3	$16.42	5.343%	$17.2973	$17.30	$17.30	$17.30
Purchase #4	$45.89	5.578%	$48.4497	$48.45	$48.45	$48.40
Purchase #5	$116.65	11.642%	$130.2304	$130.23	$130.25	$130.20
Purchase #6	$39.95	13.286%	$45.2578	$45.26	$45.25	$45.30
Purchase #7	$143.96	7.530%	$154.8002	$154.80	$154.80	$154.80
7 purchase totals =	$703.55		$763.8511	$763.85	$763.90	$763.80