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	$139.79	4.805%	$146.5069	$146.51	$146.50	$146.50
Purchase #2	$220.35	5.697%	$232.9033	$232.90	$232.90	$232.90
Purchase #3	$44.28	4.495%	$46.2704	$46.27	$46.25	$46.30
Purchase #4	$249.61	11.590%	$278.5398	$278.54	$278.55	$278.50
Purchase #5	$139.69	6.127%	$148.2488	$148.25	$148.25	$148.20
Purchase #6	$124.67	11.654%	$139.199	$139.20	$139.20	$139.20
Purchase #7	$100.46	3.300%	$103.7752	$103.78	$103.80	$103.80
7 purchase totals =	$1,018.85		$1,095.4434	$1,095.45	$1,095.45	$1,095.40