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	$23.49	7.498%	$25.2513	$25.25	$25.25	$25.30
Purchase #2	$110.83	7.515%	$119.1589	$119.16	$119.15	$119.20
Purchase #3	$178.89	9.612%	$196.0849	$196.08	$196.10	$196.10
Purchase #4	$91.58	13.298%	$103.7583	$103.76	$103.75	$103.80
Purchase #5	$138.30	10.733%	$153.1437	$153.14	$153.15	$153.10
Purchase #6	$109.94	7.191%	$117.8458	$117.85	$117.85	$117.80
Purchase #7	$196.59	13.582%	$223.2909	$223.29	$223.30	$223.30
7 purchase totals =	$849.62		$938.5338	$938.53	$938.55	$938.60