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	$139.93	3.547%	$144.8933	$144.89	$144.90	$144.90
Purchase #2	$85.65	5.417%	$90.2897	$90.29	$90.30	$90.30
Purchase #3	$122.43	3.618%	$126.8595	$126.86	$126.85	$126.90
Purchase #4	$46.99	11.537%	$52.4112	$52.41	$52.40	$52.40
Purchase #5	$115.91	8.784%	$126.0915	$126.09	$126.10	$126.10
Purchase #6	$105.78	10.192%	$116.5611	$116.56	$116.55	$116.60
Purchase #7	$232.60	13.566%	$264.1545	$264.15	$264.15	$264.20
7 purchase totals =	$849.29		$921.2608	$921.25	$921.25	$921.40