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	$219.72	4.598%	$229.8227	$229.82	$229.80	$229.80
Purchase #2	$53.61	11.656%	$59.8588	$59.86	$59.85	$59.90
Purchase #3	$156.66	10.684%	$173.3976	$173.40	$173.40	$173.40
Purchase #4	$101.99	9.272%	$111.4465	$111.45	$111.45	$111.40
Purchase #5	$226.53	7.452%	$243.411	$243.41	$243.40	$243.40
Purchase #6	$104.48	6.429%	$111.197	$111.20	$111.20	$111.20
Purchase #7	$153.95	10.469%	$170.067	$170.07	$170.05	$170.10
7 purchase totals =	$1,016.94		$1,099.2006	$1,099.21	$1,099.15	$1,099.20