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	$138.95	11.309%	$154.6639	$154.66	$154.65	$154.70
Purchase #2	$53.68	3.696%	$55.664	$55.66	$55.65	$55.70
Purchase #3	$240.28	6.648%	$256.2538	$256.25	$256.25	$256.30
Purchase #4	$150.72	3.843%	$156.5122	$156.51	$156.50	$156.50
Purchase #5	$140.39	7.643%	$151.12	$151.12	$151.10	$151.10
Purchase #6	$157.80	4.415%	$164.7669	$164.77	$164.75	$164.80
Purchase #7	$111.69	4.219%	$116.4022	$116.40	$116.40	$116.40
7 purchase totals =	$993.51		$1,055.3830	$1,055.37	$1,055.30	$1,055.50