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	$98.87	10.471%	$109.2227	$109.22	$109.20	$109.20
Purchase #2	$57.75	3.419%	$59.7245	$59.72	$59.70	$59.70
Purchase #3	$173.95	12.177%	$195.1319	$195.13	$195.15	$195.10
Purchase #4	$101.62	7.795%	$109.5413	$109.54	$109.55	$109.50
Purchase #5	$184.82	6.123%	$196.1365	$196.14	$196.15	$196.10
Purchase #6	$47.90	12.347%	$53.8142	$53.81	$53.80	$53.80
Purchase #7	$157.98	13.733%	$179.6754	$179.68	$179.70	$179.70
7 purchase totals =	$822.89		$903.2465	$903.24	$903.25	$903.10