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	$167.63	3.717%	$173.8608	$173.86	$173.85	$173.90
Purchase #2	$15.89	9.741%	$17.4378	$17.44	$17.45	$17.40
Purchase #3	$91.82	12.168%	$102.9927	$102.99	$103.00	$103.00
Purchase #4	$238.46	10.323%	$263.0762	$263.08	$263.10	$263.10
Purchase #5	$57.52	6.309%	$61.1489	$61.15	$61.15	$61.10
Purchase #6	$90.27	13.400%	$102.3662	$102.37	$102.35	$102.40
Purchase #7	$34.66	9.192%	$37.8459	$37.85	$37.85	$37.80
7 purchase totals =	$696.25		$758.7285	$758.74	$758.75	$758.70