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	$222.31	3.858%	$230.8867	$230.89	$230.90	$230.90
Purchase #2	$89.42	6.627%	$95.3459	$95.35	$95.35	$95.30
Purchase #3	$112.86	4.294%	$117.7062	$117.71	$117.70	$117.70
Purchase #4	$39.78	11.379%	$44.3066	$44.31	$44.30	$44.30
Purchase #5	$47.67	9.370%	$52.1367	$52.14	$52.15	$52.10
Purchase #6	$6.66	3.417%	$6.8876	$6.89	$6.90	$6.90
Purchase #7	$70.82	11.166%	$78.7278	$78.73	$78.75	$78.70
7 purchase totals =	$589.52		$625.9975	$626.02	$626.05	$625.90