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	$46.96	13.629%	$53.3602	$53.36	$53.35	$53.40
Purchase #2	$120.31	9.501%	$131.7407	$131.74	$131.75	$131.70
Purchase #3	$157.48	9.497%	$172.4359	$172.44	$172.45	$172.40
Purchase #4	$209.69	6.103%	$222.4874	$222.49	$222.50	$222.50
Purchase #5	$85.81	8.156%	$92.8087	$92.81	$92.80	$92.80
Purchase #6	$182.41	10.326%	$201.2457	$201.25	$201.25	$201.20
Purchase #7	$190.70	9.267%	$208.3722	$208.37	$208.35	$208.40
7 purchase totals =	$993.36		$1,082.4508	$1,082.46	$1,082.45	$1,082.40