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	$62.77	9.153%	$68.5153	$68.52	$68.50	$68.50
Purchase #2	$55.74	6.324%	$59.265	$59.27	$59.25	$59.30
Purchase #3	$211.87	12.741%	$238.8644	$238.86	$238.85	$238.90
Purchase #4	$19.88	11.172%	$22.101	$22.10	$22.10	$22.10
Purchase #5	$208.53	9.773%	$228.9096	$228.91	$228.90	$228.90
Purchase #6	$150.27	3.514%	$155.5505	$155.55	$155.55	$155.60
Purchase #7	$91.36	3.566%	$94.6179	$94.62	$94.60	$94.60
7 purchase totals =	$800.42		$867.8237	$867.83	$867.75	$867.90