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	$105.38	6.122%	$111.8314	$111.83	$111.85	$111.80
Purchase #2	$229.64	4.279%	$239.4663	$239.47	$239.45	$239.50
Purchase #3	$53.37	12.365%	$59.9692	$59.97	$59.95	$60.00
Purchase #4	$123.27	7.267%	$132.228	$132.23	$132.25	$132.20
Purchase #5	$30.29	9.379%	$33.1309	$33.13	$33.15	$33.10
Purchase #6	$170.75	12.688%	$192.4148	$192.41	$192.40	$192.40
Purchase #7	$99.63	13.719%	$113.2982	$113.30	$113.30	$113.30
7 purchase totals =	$812.33		$882.3388	$882.34	$882.35	$882.30