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	$79.43	8.286%	$86.0116	$86.01	$86.00	$86.00
Purchase #2	$106.92	11.265%	$118.9645	$118.96	$118.95	$119.00
Purchase #3	$241.66	4.784%	$253.221	$253.22	$253.20	$253.20
Purchase #4	$54.60	12.681%	$61.5238	$61.52	$61.50	$61.50
Purchase #5	$104.94	8.121%	$113.4622	$113.46	$113.45	$113.50
Purchase #6	$43.42	4.141%	$45.218	$45.22	$45.20	$45.20
Purchase #7	$221.93	12.478%	$249.6224	$249.62	$249.60	$249.60
7 purchase totals =	$852.90		$928.0235	$928.01	$927.90	$928.00