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	$92.67	11.727%	$103.5374	$103.54	$103.55	$103.50
Purchase #2	$103.86	11.789%	$116.1041	$116.10	$116.10	$116.10
Purchase #3	$170.98	11.780%	$191.1214	$191.12	$191.10	$191.10
Purchase #4	$108.66	8.694%	$118.1069	$118.11	$118.10	$118.10
Purchase #5	$83.73	8.226%	$90.6176	$90.62	$90.60	$90.60
Purchase #6	$50.95	11.716%	$56.9193	$56.92	$56.90	$56.90
Purchase #7	$51.76	4.664%	$54.1741	$54.17	$54.15	$54.20
7 purchase totals =	$662.61		$730.5808	$730.58	$730.50	$730.50