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	$212.92	4.384%	$222.2544	$222.25	$222.25	$222.30
Purchase #2	$163.47	12.855%	$184.4841	$184.48	$184.50	$184.50
Purchase #3	$176.45	7.420%	$189.5426	$189.54	$189.55	$189.50
Purchase #4	$152.36	4.203%	$158.7637	$158.76	$158.75	$158.80
Purchase #5	$200.95	4.698%	$210.3906	$210.39	$210.40	$210.40
Purchase #6	$31.46	3.753%	$32.6407	$32.64	$32.65	$32.60
Purchase #7	$148.66	7.197%	$159.3591	$159.36	$159.35	$159.40
7 purchase totals =	$1,086.27		$1,157.4352	$1,157.42	$1,157.45	$1,157.50