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	$244.91	11.605%	$273.3318	$273.33	$273.35	$273.30
Purchase #2	$33.58	11.566%	$37.4639	$37.46	$37.45	$37.50
Purchase #3	$155.54	10.813%	$172.3585	$172.36	$172.35	$172.40
Purchase #4	$211.65	13.611%	$240.4577	$240.46	$240.45	$240.50
Purchase #5	$9.82	7.376%	$10.5443	$10.54	$10.55	$10.50
Purchase #6	$241.56	9.531%	$264.5831	$264.58	$264.60	$264.60
Purchase #7	$50.97	7.294%	$54.6878	$54.69	$54.70	$54.70
7 purchase totals =	$948.03		$1,053.4271	$1,053.42	$1,053.45	$1,053.50