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	$22.46	11.456%	$25.033	$25.03	$25.05	$25.00
Purchase #2	$93.50	8.499%	$101.4466	$101.45	$101.45	$101.40
Purchase #3	$150.36	6.183%	$159.6568	$159.66	$159.65	$159.70
Purchase #4	$102.77	8.364%	$111.3657	$111.37	$111.35	$111.40
Purchase #5	$143.88	4.873%	$150.8913	$150.89	$150.90	$150.90
Purchase #6	$204.66	6.289%	$217.5311	$217.53	$217.55	$217.50
Purchase #7	$200.60	8.323%	$217.2959	$217.30	$217.30	$217.30
7 purchase totals =	$918.23		$983.2204	$983.23	$983.25	$983.20