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	$48.95	11.377%	$54.519	$54.52	$54.50	$54.50
Purchase #2	$141.78	12.538%	$159.5564	$159.56	$159.55	$159.60
Purchase #3	$57.93	4.667%	$60.6336	$60.63	$60.65	$60.60
Purchase #4	$213.61	4.148%	$222.4705	$222.47	$222.45	$222.50
Purchase #5	$159.36	10.390%	$175.9175	$175.92	$175.90	$175.90
Purchase #6	$239.37	8.669%	$260.121	$260.12	$260.10	$260.10
Purchase #7	$130.59	3.305%	$134.906	$134.91	$134.90	$134.90
7 purchase totals =	$991.59		$1,068.1240	$1,068.13	$1,068.05	$1,068.10