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	$182.69	5.567%	$192.8604	$192.86	$192.85	$192.90
Purchase #2	$190.30	8.208%	$205.9198	$205.92	$205.90	$205.90
Purchase #3	$55.49	4.287%	$57.8689	$57.87	$57.85	$57.90
Purchase #4	$151.80	8.269%	$164.3523	$164.35	$164.35	$164.40
Purchase #5	$11.38	9.275%	$12.4355	$12.44	$12.45	$12.40
Purchase #6	$94.95	4.267%	$99.0015	$99.00	$99.00	$99.00
Purchase #7	$49.73	10.375%	$54.8895	$54.89	$54.90	$54.90
7 purchase totals =	$736.34		$787.3279	$787.33	$787.30	$787.40