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	$157.38	10.311%	$173.6075	$173.61	$173.60	$173.60
Purchase #2	$120.97	8.211%	$130.9028	$130.90	$130.90	$130.90
Purchase #3	$61.47	9.735%	$67.4541	$67.45	$67.45	$67.50
Purchase #4	$82.35	9.720%	$90.3544	$90.35	$90.35	$90.40
Purchase #5	$117.77	7.278%	$126.3413	$126.34	$126.35	$126.30
Purchase #6	$39.47	10.688%	$43.6886	$43.69	$43.70	$43.70
Purchase #7	$162.50	8.441%	$176.2166	$176.22	$176.20	$176.20
7 purchase totals =	$741.91		$808.5653	$808.56	$808.55	$808.60