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	$87.46	8.805%	$95.1609	$95.16	$95.15	$95.20
Purchase #2	$77.66	11.718%	$86.7602	$86.76	$86.75	$86.80
Purchase #3	$71.52	9.512%	$78.323	$78.32	$78.30	$78.30
Purchase #4	$240.49	6.580%	$256.3142	$256.31	$256.30	$256.30
Purchase #5	$209.46	10.246%	$230.9213	$230.92	$230.90	$230.90
Purchase #6	$29.73	7.164%	$31.8599	$31.86	$31.85	$31.90
Purchase #7	$163.66	8.450%	$177.4893	$177.49	$177.50	$177.50
7 purchase totals =	$879.98		$956.8288	$956.82	$956.75	$956.90