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	$147.86	3.209%	$152.6048	$152.60	$152.60	$152.60
Purchase #2	$121.51	9.132%	$132.6063	$132.61	$132.60	$132.60
Purchase #3	$149.97	13.280%	$169.886	$169.89	$169.90	$169.90
Purchase #4	$220.71	10.447%	$243.7676	$243.77	$243.75	$243.80
Purchase #5	$43.97	5.658%	$46.4578	$46.46	$46.45	$46.50
Purchase #6	$122.70	4.252%	$127.9172	$127.92	$127.90	$127.90
Purchase #7	$18.78	11.131%	$20.8704	$20.87	$20.85	$20.90
7 purchase totals =	$825.50		$894.1101	$894.12	$894.05	$894.20