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	$163.81	6.579%	$174.5871	$174.59	$174.60	$174.60
Purchase #2	$33.90	9.822%	$37.2297	$37.23	$37.25	$37.20
Purchase #3	$95.75	5.797%	$101.3006	$101.30	$101.30	$101.30
Purchase #4	$12.27	7.580%	$13.2001	$13.20	$13.20	$13.20
Purchase #5	$242.27	12.142%	$271.6864	$271.69	$271.70	$271.70
Purchase #6	$40.60	6.244%	$43.1351	$43.14	$43.15	$43.10
Purchase #7	$85.82	12.175%	$96.2686	$96.27	$96.25	$96.30
7 purchase totals =	$674.42		$737.4076	$737.42	$737.45	$737.40