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	$116.48	9.798%	$127.8927	$127.89	$127.90	$127.90
Purchase #2	$41.92	6.136%	$44.4922	$44.49	$44.50	$44.50
Purchase #3	$176.26	6.144%	$187.0894	$187.09	$187.10	$187.10
Purchase #4	$173.28	3.613%	$179.5406	$179.54	$179.55	$179.50
Purchase #5	$77.86	4.172%	$81.1083	$81.11	$81.10	$81.10
Purchase #6	$241.90	6.113%	$256.6873	$256.69	$256.70	$256.70
Purchase #7	$163.26	6.112%	$173.2385	$173.24	$173.25	$173.20
7 purchase totals =	$990.96		$1,050.0490	$1,050.05	$1,050.10	$1,050.00