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	$146.70	9.124%	$160.0849	$160.08	$160.10	$160.10
Purchase #2	$138.59	3.579%	$143.5501	$143.55	$143.55	$143.60
Purchase #3	$42.77	12.711%	$48.2065	$48.21	$48.20	$48.20
Purchase #4	$249.58	13.580%	$283.473	$283.47	$283.45	$283.50
Purchase #5	$97.31	3.276%	$100.4979	$100.50	$100.50	$100.50
Purchase #6	$86.26	10.392%	$95.2241	$95.22	$95.20	$95.20
Purchase #7	$98.77	12.595%	$111.2101	$111.21	$111.20	$111.20
7 purchase totals =	$859.98		$942.2466	$942.24	$942.20	$942.30