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	$241.47	3.669%	$250.3295	$250.33	$250.35	$250.30
Purchase #2	$88.54	10.689%	$98.004	$98.00	$98.00	$98.00
Purchase #3	$49.64	10.711%	$54.9569	$54.96	$54.95	$55.00
Purchase #4	$185.94	12.105%	$208.448	$208.45	$208.45	$208.40
Purchase #5	$86.28	3.601%	$89.3869	$89.39	$89.40	$89.40
Purchase #6	$238.94	5.252%	$251.4891	$251.49	$251.50	$251.50
Purchase #7	$103.69	4.691%	$108.5541	$108.55	$108.55	$108.60
7 purchase totals =	$994.50		$1,061.1685	$1,061.17	$1,061.20	$1,061.20