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	$233.77	11.723%	$261.1749	$261.17	$261.15	$261.20
Purchase #2	$211.92	4.343%	$221.1237	$221.12	$221.10	$221.10
Purchase #3	$85.26	5.351%	$89.8223	$89.82	$89.80	$89.80
Purchase #4	$142.28	4.383%	$148.5161	$148.52	$148.50	$148.50
Purchase #5	$156.78	12.500%	$176.3775	$176.38	$176.40	$176.40
Purchase #6	$39.26	10.644%	$43.4388	$43.44	$43.45	$43.40
Purchase #7	$52.96	11.765%	$59.1907	$59.19	$59.20	$59.20
7 purchase totals =	$922.23		$999.6440	$999.64	$999.60	$999.60