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	$98.55	6.679%	$105.1322	$105.13	$105.15	$105.10
Purchase #2	$128.68	8.579%	$139.7195	$139.72	$139.70	$139.70
Purchase #3	$242.39	13.598%	$275.3502	$275.35	$275.35	$275.40
Purchase #4	$143.94	7.436%	$154.6434	$154.64	$154.65	$154.60
Purchase #5	$98.38	8.617%	$106.8574	$106.86	$106.85	$106.90
Purchase #6	$13.43	8.817%	$14.6141	$14.61	$14.60	$14.60
Purchase #7	$227.86	7.185%	$244.2317	$244.23	$244.25	$244.20
7 purchase totals =	$953.23		$1,040.5485	$1,040.54	$1,040.55	$1,040.50