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	$49.93	4.524%	$52.1888	$52.19	$52.20	$52.20
Purchase #2	$131.36	11.274%	$146.1695	$146.17	$146.15	$146.20
Purchase #3	$138.30	10.270%	$152.5034	$152.50	$152.50	$152.50
Purchase #4	$103.91	7.308%	$111.5037	$111.50	$111.50	$111.50
Purchase #5	$158.43	9.124%	$172.8852	$172.89	$172.90	$172.90
Purchase #6	$169.71	9.118%	$185.1842	$185.18	$185.20	$185.20
Purchase #7	$11.47	4.441%	$11.9794	$11.98	$12.00	$12.00
7 purchase totals =	$763.11		$832.4142	$832.41	$832.45	$832.50