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	$195.89	9.529%	$214.5564	$214.56	$214.55	$214.60
Purchase #2	$145.66	13.857%	$165.8441	$165.84	$165.85	$165.80
Purchase #3	$205.79	8.234%	$222.7347	$222.73	$222.75	$222.70
Purchase #4	$32.25	13.561%	$36.6234	$36.62	$36.60	$36.60
Purchase #5	$97.27	9.254%	$106.2714	$106.27	$106.25	$106.30
Purchase #6	$200.47	10.471%	$221.4612	$221.46	$221.45	$221.50
Purchase #7	$224.78	13.593%	$255.3343	$255.33	$255.35	$255.30
7 purchase totals =	$1,102.11		$1,222.8255	$1,222.81	$1,222.80	$1,222.80