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	$159.98	4.505%	$167.1871	$167.19	$167.20	$167.20
Purchase #2	$29.30	10.581%	$32.4002	$32.40	$32.40	$32.40
Purchase #3	$214.27	6.131%	$227.4069	$227.41	$227.40	$227.40
Purchase #4	$140.57	12.826%	$158.5995	$158.60	$158.60	$158.60
Purchase #5	$244.77	11.643%	$273.2686	$273.27	$273.25	$273.30
Purchase #6	$75.94	6.475%	$80.8571	$80.86	$80.85	$80.90
Purchase #7	$100.31	12.375%	$112.7234	$112.72	$112.70	$112.70
7 purchase totals =	$965.14		$1,052.4428	$1,052.45	$1,052.40	$1,052.50