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	$162.26	6.292%	$172.4694	$172.47	$172.45	$172.50
Purchase #2	$165.95	10.627%	$183.5855	$183.59	$183.60	$183.60
Purchase #3	$232.99	11.536%	$259.8677	$259.87	$259.85	$259.90
Purchase #4	$105.98	6.787%	$113.1729	$113.17	$113.15	$113.20
Purchase #5	$23.30	5.254%	$24.5242	$24.52	$24.50	$24.50
Purchase #6	$245.33	5.362%	$258.4846	$258.48	$258.50	$258.50
Purchase #7	$95.73	4.638%	$100.17	$100.17	$100.15	$100.20
7 purchase totals =	$1,031.54		$1,112.2743	$1,112.27	$1,112.20	$1,112.40