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	$79.68	7.242%	$85.4504	$85.45	$85.45	$85.50
Purchase #2	$42.79	4.793%	$44.8409	$44.84	$44.85	$44.80
Purchase #3	$111.86	9.718%	$122.7306	$122.73	$122.75	$122.70
Purchase #4	$68.86	13.667%	$78.2711	$78.27	$78.25	$78.30
Purchase #5	$93.25	7.805%	$100.5282	$100.53	$100.55	$100.50
Purchase #6	$219.91	6.398%	$233.9798	$233.98	$234.00	$234.00
Purchase #7	$202.74	13.284%	$229.672	$229.67	$229.65	$229.70
7 purchase totals =	$819.09		$895.4730	$895.47	$895.50	$895.50