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	$64.72	4.205%	$67.4415	$67.44	$67.45	$67.40
Purchase #2	$27.92	7.638%	$30.0525	$30.05	$30.05	$30.10
Purchase #3	$109.40	7.476%	$117.5787	$117.58	$117.60	$117.60
Purchase #4	$181.89	10.241%	$200.5174	$200.52	$200.50	$200.50
Purchase #5	$95.65	13.205%	$108.2806	$108.28	$108.30	$108.30
Purchase #6	$133.72	13.484%	$151.7508	$151.75	$151.75	$151.80
Purchase #7	$142.57	12.681%	$160.6493	$160.65	$160.65	$160.60
7 purchase totals =	$755.87		$836.2708	$836.27	$836.30	$836.30