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	$212.45	8.187%	$229.8433	$229.84	$229.85	$229.80
Purchase #2	$22.52	4.685%	$23.5751	$23.58	$23.60	$23.60
Purchase #3	$79.49	7.665%	$85.5829	$85.58	$85.60	$85.60
Purchase #4	$185.96	12.650%	$209.4839	$209.48	$209.50	$209.50
Purchase #5	$56.59	6.308%	$60.1597	$60.16	$60.15	$60.20
Purchase #6	$90.32	10.653%	$99.9418	$99.94	$99.95	$99.90
Purchase #7	$172.34	8.631%	$187.2147	$187.21	$187.20	$187.20
7 purchase totals =	$819.67		$895.8014	$895.79	$895.85	$895.80