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	$201.28	7.102%	$215.5749	$215.57	$215.55	$215.60
Purchase #2	$82.66	7.700%	$89.0248	$89.02	$89.00	$89.00
Purchase #3	$244.86	3.476%	$253.3713	$253.37	$253.35	$253.40
Purchase #4	$211.67	10.494%	$233.8826	$233.88	$233.90	$233.90
Purchase #5	$113.38	13.382%	$128.5525	$128.55	$128.55	$128.60
Purchase #6	$158.51	5.169%	$166.7034	$166.70	$166.70	$166.70
Purchase #7	$155.74	6.719%	$166.2042	$166.20	$166.20	$166.20
7 purchase totals =	$1,168.10		$1,253.3137	$1,253.29	$1,253.25	$1,253.40