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	$163.61	10.229%	$180.3457	$180.35	$180.35	$180.30
Purchase #2	$204.87	8.814%	$222.9272	$222.93	$222.95	$222.90
Purchase #3	$229.94	3.556%	$238.1167	$238.12	$238.10	$238.10
Purchase #4	$41.43	4.860%	$43.4435	$43.44	$43.45	$43.40
Purchase #5	$223.67	10.326%	$246.7662	$246.77	$246.75	$246.80
Purchase #6	$155.49	10.163%	$171.2924	$171.29	$171.30	$171.30
Purchase #7	$141.38	8.468%	$153.3521	$153.35	$153.35	$153.40
7 purchase totals =	$1,160.39		$1,256.2438	$1,256.25	$1,256.25	$1,256.20