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	$7.25	5.435%	$7.644	$7.64	$7.65	$7.60
Purchase #2	$35.80	6.767%	$38.2226	$38.22	$38.20	$38.20
Purchase #3	$225.66	8.242%	$244.2589	$244.26	$244.25	$244.30
Purchase #4	$152.41	13.723%	$173.3252	$173.33	$173.35	$173.30
Purchase #5	$28.71	10.289%	$31.664	$31.66	$31.65	$31.70
Purchase #6	$219.54	9.799%	$241.0527	$241.05	$241.05	$241.10
Purchase #7	$85.39	4.249%	$89.0182	$89.02	$89.00	$89.00
7 purchase totals =	$754.76		$825.1856	$825.18	$825.15	$825.20