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	$132.56	10.220%	$146.1076	$146.11	$146.10	$146.10
Purchase #2	$36.26	10.748%	$40.1572	$40.16	$40.15	$40.20
Purchase #3	$72.78	5.329%	$76.6584	$76.66	$76.65	$76.70
Purchase #4	$185.48	11.684%	$207.1515	$207.15	$207.15	$207.20
Purchase #5	$96.33	5.401%	$101.5328	$101.53	$101.55	$101.50
Purchase #6	$30.72	8.816%	$33.4283	$33.43	$33.45	$33.40
Purchase #7	$123.64	10.383%	$136.4775	$136.48	$136.50	$136.50
7 purchase totals =	$677.77		$741.5133	$741.52	$741.55	$741.60