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	$17.46	4.805%	$18.299	$18.30	$18.30	$18.30
Purchase #2	$11.97	7.180%	$12.8294	$12.83	$12.85	$12.80
Purchase #3	$151.33	7.645%	$162.8992	$162.90	$162.90	$162.90
Purchase #4	$31.79	7.240%	$34.0916	$34.09	$34.10	$34.10
Purchase #5	$69.53	12.581%	$78.2776	$78.28	$78.30	$78.30
Purchase #6	$149.74	13.629%	$170.1481	$170.15	$170.15	$170.10
Purchase #7	$167.41	10.776%	$185.4501	$185.45	$185.45	$185.50
7 purchase totals =	$599.23		$661.9950	$662.00	$662.05	$662.00