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	$95.31	5.384%	$100.4415	$100.44	$100.45	$100.40
Purchase #2	$63.30	5.684%	$66.898	$66.90	$66.90	$66.90
Purchase #3	$48.39	13.278%	$54.8152	$54.82	$54.80	$54.80
Purchase #4	$144.91	7.557%	$155.8608	$155.86	$155.85	$155.90
Purchase #5	$31.38	9.491%	$34.3583	$34.36	$34.35	$34.40
Purchase #6	$222.61	4.766%	$233.2196	$233.22	$233.20	$233.20
Purchase #7	$124.96	8.682%	$135.809	$135.81	$135.80	$135.80
7 purchase totals =	$730.86		$781.4024	$781.41	$781.35	$781.40