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	$122.63	3.611%	$127.0582	$127.06	$127.05	$127.10
Purchase #2	$84.99	5.321%	$89.5123	$89.51	$89.50	$89.50
Purchase #3	$140.57	3.615%	$145.6516	$145.65	$145.65	$145.70
Purchase #4	$227.76	8.160%	$246.3452	$246.35	$246.35	$246.30
Purchase #5	$19.44	5.255%	$20.4616	$20.46	$20.45	$20.50
Purchase #6	$218.63	11.838%	$244.5114	$244.51	$244.50	$244.50
Purchase #7	$201.52	3.376%	$208.3233	$208.32	$208.30	$208.30
7 purchase totals =	$1,015.54		$1,081.8636	$1,081.86	$1,081.80	$1,081.90