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	$51.39	7.249%	$55.1153	$55.12	$55.10	$55.10
Purchase #2	$94.33	7.707%	$101.6	$101.60	$101.60	$101.60
Purchase #3	$207.65	7.616%	$223.4646	$223.46	$223.45	$223.50
Purchase #4	$183.96	5.504%	$194.0852	$194.09	$194.10	$194.10
Purchase #5	$217.41	4.712%	$227.6544	$227.65	$227.65	$227.70
Purchase #6	$80.46	3.528%	$83.2986	$83.30	$83.30	$83.30
Purchase #7	$186.78	7.169%	$200.1703	$200.17	$200.15	$200.20
7 purchase totals =	$1,021.98		$1,085.3884	$1,085.39	$1,085.35	$1,085.50