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	$203.65	3.838%	$211.4661	$211.47	$211.45	$211.50
Purchase #2	$60.78	11.416%	$67.7186	$67.72	$67.70	$67.70
Purchase #3	$111.81	9.544%	$122.4811	$122.48	$122.50	$122.50
Purchase #4	$158.71	4.414%	$165.7155	$165.72	$165.70	$165.70
Purchase #5	$172.59	5.245%	$181.6423	$181.64	$181.65	$181.60
Purchase #6	$160.92	6.354%	$171.1449	$171.14	$171.15	$171.10
Purchase #7	$120.83	8.339%	$130.906	$130.91	$130.90	$130.90
7 purchase totals =	$989.29		$1,051.0745	$1,051.08	$1,051.05	$1,051.00