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	$245.74	3.540%	$254.4392	$254.44	$254.45	$254.40
Purchase #2	$225.88	7.836%	$243.58	$243.58	$243.60	$243.60
Purchase #3	$131.93	3.196%	$136.1465	$136.15	$136.15	$136.10
Purchase #4	$136.54	10.825%	$151.3205	$151.32	$151.30	$151.30
Purchase #5	$224.42	13.286%	$254.2364	$254.24	$254.25	$254.20
Purchase #6	$111.95	10.599%	$123.8156	$123.82	$123.80	$123.80
Purchase #7	$37.77	4.528%	$39.4802	$39.48	$39.50	$39.50
7 purchase totals =	$1,114.23		$1,203.0184	$1,203.03	$1,203.05	$1,202.90