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	$153.31	6.159%	$162.7524	$162.75	$162.75	$162.80
Purchase #2	$68.35	6.176%	$72.5713	$72.57	$72.55	$72.60
Purchase #3	$238.86	12.667%	$269.1164	$269.12	$269.10	$269.10
Purchase #4	$37.92	5.450%	$39.9866	$39.99	$40.00	$40.00
Purchase #5	$154.84	7.605%	$166.6156	$166.62	$166.60	$166.60
Purchase #6	$43.58	3.663%	$45.1763	$45.18	$45.20	$45.20
Purchase #7	$25.54	11.368%	$28.4434	$28.44	$28.45	$28.40
7 purchase totals =	$722.40		$784.6620	$784.67	$784.65	$784.70