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	$208.43	6.617%	$222.2218	$222.22	$222.20	$222.20
Purchase #2	$170.85	5.531%	$180.2997	$180.30	$180.30	$180.30
Purchase #3	$232.38	4.165%	$242.0586	$242.06	$242.05	$242.10
Purchase #4	$169.52	5.859%	$179.4522	$179.45	$179.45	$179.50
Purchase #5	$144.34	4.332%	$150.5928	$150.59	$150.60	$150.60
Purchase #6	$133.35	12.667%	$150.2414	$150.24	$150.25	$150.20
Purchase #7	$67.99	4.784%	$71.2426	$71.24	$71.25	$71.20
7 purchase totals =	$1,126.86		$1,196.1091	$1,196.10	$1,196.10	$1,196.10