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	$247.85	7.397%	$266.1835	$266.18	$266.20	$266.20
Purchase #2	$20.78	13.339%	$23.5518	$23.55	$23.55	$23.60
Purchase #3	$127.42	9.179%	$139.1159	$139.12	$139.10	$139.10
Purchase #4	$11.40	3.174%	$11.7618	$11.76	$11.75	$11.80
Purchase #5	$49.35	10.442%	$54.5031	$54.50	$54.50	$54.50
Purchase #6	$202.88	13.142%	$229.5425	$229.54	$229.55	$229.50
Purchase #7	$91.98	8.816%	$100.089	$100.09	$100.10	$100.10
7 purchase totals =	$751.66		$824.7476	$824.74	$824.75	$824.80