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	$61.77	8.576%	$67.0674	$67.07	$67.05	$67.10
Purchase #2	$54.77	5.270%	$57.6564	$57.66	$57.65	$57.70
Purchase #3	$115.33	8.684%	$125.3453	$125.35	$125.35	$125.30
Purchase #4	$173.33	4.581%	$181.2702	$181.27	$181.25	$181.30
Purchase #5	$173.59	6.344%	$184.6025	$184.60	$184.60	$184.60
Purchase #6	$33.55	11.826%	$37.5176	$37.52	$37.50	$37.50
Purchase #7	$42.26	10.283%	$46.6056	$46.61	$46.60	$46.60
7 purchase totals =	$654.60		$700.0650	$700.08	$700.00	$700.10