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	$160.77	5.223%	$169.167	$169.17	$169.15	$169.20
Purchase #2	$155.32	10.780%	$172.0635	$172.06	$172.05	$172.10
Purchase #3	$151.57	11.197%	$168.5413	$168.54	$168.55	$168.50
Purchase #4	$235.34	4.641%	$246.2621	$246.26	$246.25	$246.30
Purchase #5	$123.33	7.143%	$132.1395	$132.14	$132.15	$132.10
Purchase #6	$242.51	12.854%	$273.6822	$273.68	$273.70	$273.70
Purchase #7	$235.76	13.511%	$267.6135	$267.61	$267.60	$267.60
7 purchase totals =	$1,304.60		$1,429.4691	$1,429.46	$1,429.45	$1,429.50