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	$215.92	8.230%	$233.6902	$233.69	$233.70	$233.70
Purchase #2	$147.86	3.375%	$152.8503	$152.85	$152.85	$152.90
Purchase #3	$217.28	3.456%	$224.7892	$224.79	$224.80	$224.80
Purchase #4	$10.46	9.113%	$11.4132	$11.41	$11.40	$11.40
Purchase #5	$6.38	8.414%	$6.9168	$6.92	$6.90	$6.90
Purchase #6	$40.98	10.559%	$45.3071	$45.31	$45.30	$45.30
Purchase #7	$88.92	6.220%	$94.4508	$94.45	$94.45	$94.50
7 purchase totals =	$727.80		$769.4176	$769.42	$769.40	$769.50