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	$41.74	5.213%	$43.9159	$43.92	$43.90	$43.90
Purchase #2	$192.93	6.812%	$206.0724	$206.07	$206.05	$206.10
Purchase #3	$166.37	3.512%	$172.2129	$172.21	$172.20	$172.20
Purchase #4	$191.56	4.154%	$199.5174	$199.52	$199.50	$199.50
Purchase #5	$165.42	4.509%	$172.8788	$172.88	$172.90	$172.90
Purchase #6	$170.86	8.520%	$185.4173	$185.42	$185.40	$185.40
Purchase #7	$90.29	10.873%	$100.1072	$100.11	$100.10	$100.10
7 purchase totals =	$1,019.17		$1,080.1219	$1,080.13	$1,080.05	$1,080.10