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	$96.42	3.553%	$99.8458	$99.85	$99.85	$99.80
Purchase #2	$136.92	13.532%	$155.448	$155.45	$155.45	$155.40
Purchase #3	$125.35	4.603%	$131.1199	$131.12	$131.10	$131.10
Purchase #4	$229.96	12.530%	$258.774	$258.77	$258.75	$258.80
Purchase #5	$14.33	3.572%	$14.8419	$14.84	$14.85	$14.80
Purchase #6	$167.39	12.112%	$187.6643	$187.66	$187.65	$187.70
Purchase #7	$159.67	10.170%	$175.9084	$175.91	$175.90	$175.90
7 purchase totals =	$930.04		$1,023.6023	$1,023.60	$1,023.55	$1,023.50