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	$62.53	6.670%	$66.7008	$66.70	$66.70	$66.70
Purchase #2	$201.26	10.440%	$222.2715	$222.27	$222.25	$222.30
Purchase #3	$107.28	5.842%	$113.5473	$113.55	$113.55	$113.50
Purchase #4	$116.53	4.229%	$121.4581	$121.46	$121.45	$121.50
Purchase #5	$195.98	11.353%	$218.2296	$218.23	$218.25	$218.20
Purchase #6	$244.38	4.845%	$256.2202	$256.22	$256.20	$256.20
Purchase #7	$89.31	6.213%	$94.8588	$94.86	$94.85	$94.90
7 purchase totals =	$1,017.27		$1,093.2863	$1,093.29	$1,093.25	$1,093.30