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	$162.29	6.270%	$172.4656	$172.47	$172.45	$172.50
Purchase #2	$8.44	13.750%	$9.6005	$9.60	$9.60	$9.60
Purchase #3	$199.89	12.297%	$224.4705	$224.47	$224.45	$224.50
Purchase #4	$148.47	6.705%	$158.4249	$158.42	$158.40	$158.40
Purchase #5	$37.74	11.522%	$42.0884	$42.09	$42.10	$42.10
Purchase #6	$117.33	6.361%	$124.7934	$124.79	$124.80	$124.80
Purchase #7	$38.44	4.872%	$40.3128	$40.31	$40.30	$40.30
7 purchase totals =	$712.60		$772.1561	$772.15	$772.10	$772.20