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	$9.37	11.665%	$10.463	$10.46	$10.45	$10.50
Purchase #2	$115.56	13.567%	$131.238	$131.24	$131.25	$131.20
Purchase #3	$41.46	9.780%	$45.5148	$45.51	$45.50	$45.50
Purchase #4	$88.87	8.208%	$96.1644	$96.16	$96.15	$96.20
Purchase #5	$222.36	8.596%	$241.4741	$241.47	$241.45	$241.50
Purchase #6	$144.95	12.849%	$163.5746	$163.57	$163.55	$163.60
Purchase #7	$40.83	3.726%	$42.3513	$42.35	$42.35	$42.40
7 purchase totals =	$663.40		$730.7802	$730.76	$730.70	$730.90