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	$146.75	13.805%	$167.0088	$167.01	$167.00	$167.00
Purchase #2	$31.72	4.253%	$33.0691	$33.07	$33.05	$33.10
Purchase #3	$80.81	10.347%	$89.1714	$89.17	$89.15	$89.20
Purchase #4	$129.92	10.110%	$143.0549	$143.05	$143.05	$143.10
Purchase #5	$115.36	13.137%	$130.5148	$130.51	$130.50	$130.50
Purchase #6	$51.33	6.353%	$54.591	$54.59	$54.60	$54.60
Purchase #7	$121.29	13.856%	$138.0959	$138.10	$138.10	$138.10
7 purchase totals =	$677.18		$755.5059	$755.50	$755.45	$755.60