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	$86.27	4.511%	$90.1616	$90.16	$90.15	$90.20
Purchase #2	$100.54	5.649%	$106.2195	$106.22	$106.20	$106.20
Purchase #3	$185.58	12.104%	$208.0426	$208.04	$208.05	$208.00
Purchase #4	$10.41	7.213%	$11.1609	$11.16	$11.15	$11.20
Purchase #5	$98.86	12.729%	$111.4439	$111.44	$111.45	$111.40
Purchase #6	$154.30	5.624%	$162.9778	$162.98	$163.00	$163.00
Purchase #7	$34.92	9.561%	$38.2587	$38.26	$38.25	$38.30
7 purchase totals =	$670.88		$728.2650	$728.26	$728.25	$728.30