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	$19.92	4.237%	$20.764	$20.76	$20.75	$20.80
Purchase #2	$80.77	13.739%	$91.867	$91.87	$91.85	$91.90
Purchase #3	$58.35	13.105%	$65.9968	$66.00	$66.00	$66.00
Purchase #4	$41.84	8.466%	$45.3822	$45.38	$45.40	$45.40
Purchase #5	$182.26	5.770%	$192.7764	$192.78	$192.80	$192.80
Purchase #6	$133.57	8.483%	$144.9007	$144.90	$144.90	$144.90
Purchase #7	$135.35	6.467%	$144.1031	$144.10	$144.10	$144.10
7 purchase totals =	$652.06		$705.7902	$705.79	$705.80	$705.90