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	$90.44	6.643%	$96.4479	$96.45	$96.45	$96.40
Purchase #2	$96.53	13.416%	$109.4805	$109.48	$109.50	$109.50
Purchase #3	$250.94	6.463%	$267.1583	$267.16	$267.15	$267.20
Purchase #4	$198.83	12.831%	$224.3419	$224.34	$224.35	$224.30
Purchase #5	$99.51	12.494%	$111.9428	$111.94	$111.95	$111.90
Purchase #6	$228.71	12.733%	$257.8316	$257.83	$257.85	$257.80
Purchase #7	$118.62	8.855%	$129.1238	$129.12	$129.10	$129.10
7 purchase totals =	$1,083.58		$1,196.3268	$1,196.32	$1,196.35	$1,196.20