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	$107.54	6.297%	$114.3118	$114.31	$114.30	$114.30
Purchase #2	$45.44	10.121%	$50.039	$50.04	$50.05	$50.00
Purchase #3	$155.29	3.864%	$161.2904	$161.29	$161.30	$161.30
Purchase #4	$234.43	5.304%	$246.8642	$246.86	$246.85	$246.90
Purchase #5	$215.35	5.240%	$226.6343	$226.63	$226.65	$226.60
Purchase #6	$151.69	5.230%	$159.6234	$159.62	$159.60	$159.60
Purchase #7	$132.41	7.296%	$142.0706	$142.07	$142.05	$142.10
7 purchase totals =	$1,042.15		$1,100.8337	$1,100.82	$1,100.80	$1,100.80