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	$108.84	7.716%	$117.2381	$117.24	$117.25	$117.20
Purchase #2	$36.30	11.575%	$40.5017	$40.50	$40.50	$40.50
Purchase #3	$73.91	6.550%	$78.7511	$78.75	$78.75	$78.80
Purchase #4	$149.26	7.694%	$160.7441	$160.74	$160.75	$160.70
Purchase #5	$250.71	5.640%	$264.85	$264.85	$264.85	$264.90
Purchase #6	$250.36	12.469%	$281.5774	$281.58	$281.60	$281.60
Purchase #7	$34.39	10.131%	$37.8741	$37.87	$37.85	$37.90
7 purchase totals =	$903.77		$981.5365	$981.53	$981.55	$981.60