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	$126.26	3.841%	$131.1096	$131.11	$131.10	$131.10
Purchase #2	$184.25	8.765%	$200.3995	$200.40	$200.40	$200.40
Purchase #3	$237.95	5.198%	$250.3186	$250.32	$250.30	$250.30
Purchase #4	$241.68	5.735%	$255.5403	$255.54	$255.55	$255.50
Purchase #5	$7.56	10.391%	$8.3456	$8.35	$8.35	$8.30
Purchase #6	$27.40	13.278%	$31.0382	$31.04	$31.05	$31.00
Purchase #7	$127.74	3.260%	$131.9043	$131.90	$131.90	$131.90
7 purchase totals =	$952.84		$1,008.6561	$1,008.66	$1,008.65	$1,008.50