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	$77.60	11.845%	$86.7917	$86.79	$86.80	$86.80
Purchase #2	$96.81	4.852%	$101.5072	$101.51	$101.50	$101.50
Purchase #3	$48.82	11.798%	$54.5798	$54.58	$54.60	$54.60
Purchase #4	$144.69	5.867%	$153.179	$153.18	$153.20	$153.20
Purchase #5	$202.41	6.675%	$215.9209	$215.92	$215.90	$215.90
Purchase #6	$16.55	12.531%	$18.6239	$18.62	$18.60	$18.60
Purchase #7	$119.63	9.764%	$131.3107	$131.31	$131.30	$131.30
7 purchase totals =	$706.51		$761.9132	$761.91	$761.90	$761.90