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	$135.41	8.452%	$146.8549	$146.85	$146.85	$146.90
Purchase #2	$47.76	5.851%	$50.5544	$50.55	$50.55	$50.60
Purchase #3	$160.78	11.829%	$179.7987	$179.80	$179.80	$179.80
Purchase #4	$175.27	5.397%	$184.7293	$184.73	$184.75	$184.70
Purchase #5	$211.35	12.781%	$238.3626	$238.36	$238.35	$238.40
Purchase #6	$213.67	4.812%	$223.9518	$223.95	$223.95	$224.00
Purchase #7	$66.47	9.467%	$72.7627	$72.76	$72.75	$72.80
7 purchase totals =	$1,010.71		$1,097.0144	$1,097.00	$1,097.00	$1,097.20