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	$237.56	9.127%	$259.2421	$259.24	$259.25	$259.20
Purchase #2	$96.66	6.379%	$102.8259	$102.83	$102.85	$102.80
Purchase #3	$205.89	11.829%	$230.2447	$230.24	$230.25	$230.20
Purchase #4	$228.77	11.248%	$254.502	$254.50	$254.50	$254.50
Purchase #5	$38.91	8.500%	$42.2174	$42.22	$42.20	$42.20
Purchase #6	$137.27	6.379%	$146.0265	$146.03	$146.05	$146.00
Purchase #7	$18.49	10.452%	$20.4226	$20.42	$20.40	$20.40
7 purchase totals =	$963.55		$1,055.4812	$1,055.48	$1,055.50	$1,055.30