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	$49.42	11.339%	$55.0237	$55.02	$55.00	$55.00
Purchase #2	$125.39	3.295%	$129.5216	$129.52	$129.50	$129.50
Purchase #3	$7.31	7.124%	$7.8308	$7.83	$7.85	$7.80
Purchase #4	$230.63	7.421%	$247.7451	$247.75	$247.75	$247.70
Purchase #5	$158.86	8.541%	$172.4282	$172.43	$172.45	$172.40
Purchase #6	$164.46	4.248%	$171.4463	$171.45	$171.45	$171.40
Purchase #7	$89.34	13.169%	$101.1052	$101.11	$101.10	$101.10
7 purchase totals =	$825.41		$885.1009	$885.11	$885.10	$884.90