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	$153.79	11.743%	$171.8496	$171.85	$171.85	$171.80
Purchase #2	$76.38	9.763%	$83.837	$83.84	$83.85	$83.80
Purchase #3	$165.92	3.839%	$172.2897	$172.29	$172.30	$172.30
Purchase #4	$64.84	5.725%	$68.5521	$68.55	$68.55	$68.60
Purchase #5	$177.37	5.516%	$187.1537	$187.15	$187.15	$187.20
Purchase #6	$91.61	9.149%	$99.9914	$99.99	$100.00	$100.00
Purchase #7	$37.59	12.351%	$42.2327	$42.23	$42.25	$42.20
7 purchase totals =	$767.50		$825.9062	$825.90	$825.95	$825.90