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	$183.43	3.710%	$190.2353	$190.24	$190.25	$190.20
Purchase #2	$139.89	8.270%	$151.4589	$151.46	$151.45	$151.50
Purchase #3	$171.25	3.213%	$176.7523	$176.75	$176.75	$176.80
Purchase #4	$93.87	11.443%	$104.6115	$104.61	$104.60	$104.60
Purchase #5	$217.51	6.481%	$231.6068	$231.61	$231.60	$231.60
Purchase #6	$70.46	5.408%	$74.2705	$74.27	$74.25	$74.30
Purchase #7	$94.74	8.133%	$102.4452	$102.45	$102.45	$102.40
7 purchase totals =	$971.15		$1,031.3805	$1,031.39	$1,031.35	$1,031.40