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	$219.50	6.224%	$233.1617	$233.16	$233.15	$233.20
Purchase #2	$208.48	7.289%	$223.6761	$223.68	$223.70	$223.70
Purchase #3	$79.75	12.612%	$89.8081	$89.81	$89.80	$89.80
Purchase #4	$235.45	4.656%	$246.4126	$246.41	$246.40	$246.40
Purchase #5	$215.83	13.563%	$245.103	$245.10	$245.10	$245.10
Purchase #6	$40.41	5.416%	$42.5986	$42.60	$42.60	$42.60
Purchase #7	$54.66	11.471%	$60.93	$60.93	$60.95	$60.90
7 purchase totals =	$1,054.08		$1,141.6901	$1,141.69	$1,141.70	$1,141.70