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	$105.34	4.625%	$110.212	$110.21	$110.20	$110.20
Purchase #2	$78.82	13.751%	$89.6585	$89.66	$89.65	$89.70
Purchase #3	$166.79	7.689%	$179.6145	$179.61	$179.60	$179.60
Purchase #4	$101.54	4.106%	$105.7092	$105.71	$105.70	$105.70
Purchase #5	$173.86	10.660%	$192.3935	$192.39	$192.40	$192.40
Purchase #6	$11.55	4.705%	$12.0934	$12.09	$12.10	$12.10
Purchase #7	$164.80	3.847%	$171.1399	$171.14	$171.15	$171.10
7 purchase totals =	$802.70		$860.8210	$860.81	$860.80	$860.80