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	$41.93	11.157%	$46.6081	$46.61	$46.60	$46.60
Purchase #2	$110.33	9.370%	$120.6679	$120.67	$120.65	$120.70
Purchase #3	$99.66	5.431%	$105.0725	$105.07	$105.05	$105.10
Purchase #4	$48.29	10.647%	$53.4314	$53.43	$53.45	$53.40
Purchase #5	$131.77	6.185%	$139.92	$139.92	$139.90	$139.90
Purchase #6	$120.51	9.463%	$131.9139	$131.91	$131.90	$131.90
Purchase #7	$156.82	12.508%	$176.435	$176.44	$176.45	$176.40
7 purchase totals =	$709.31		$774.0488	$774.05	$774.00	$774.00