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	$214.66	4.221%	$223.7208	$223.72	$223.70	$223.70
Purchase #2	$243.61	10.158%	$268.3559	$268.36	$268.35	$268.40
Purchase #3	$104.70	4.842%	$109.7696	$109.77	$109.75	$109.80
Purchase #4	$85.25	5.776%	$90.174	$90.17	$90.15	$90.20
Purchase #5	$168.62	9.410%	$184.4871	$184.49	$184.50	$184.50
Purchase #6	$107.61	3.724%	$111.6174	$111.62	$111.60	$111.60
Purchase #7	$172.51	13.113%	$195.1312	$195.13	$195.15	$195.10
7 purchase totals =	$1,096.96		$1,183.2560	$1,183.26	$1,183.20	$1,183.30