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	$227.53	6.432%	$242.1647	$242.16	$242.15	$242.20
Purchase #2	$147.45	5.509%	$155.573	$155.57	$155.55	$155.60
Purchase #3	$227.91	4.746%	$238.7266	$238.73	$238.75	$238.70
Purchase #4	$53.61	11.325%	$59.6813	$59.68	$59.70	$59.70
Purchase #5	$169.86	6.724%	$181.2814	$181.28	$181.30	$181.30
Purchase #6	$61.65	8.753%	$67.0462	$67.05	$67.05	$67.00
Purchase #7	$68.89	3.152%	$71.0614	$71.06	$71.05	$71.10
7 purchase totals =	$956.90		$1,015.5346	$1,015.53	$1,015.55	$1,015.60