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	$108.97	11.792%	$121.8197	$121.82	$121.80	$121.80
Purchase #2	$148.35	12.555%	$166.9753	$166.98	$167.00	$167.00
Purchase #3	$191.74	3.726%	$198.8842	$198.88	$198.90	$198.90
Purchase #4	$89.65	12.111%	$100.5075	$100.51	$100.50	$100.50
Purchase #5	$202.53	8.235%	$219.2083	$219.21	$219.20	$219.20
Purchase #6	$139.36	3.209%	$143.8321	$143.83	$143.85	$143.80
Purchase #7	$171.92	10.684%	$190.2879	$190.29	$190.30	$190.30
7 purchase totals =	$1,052.52		$1,141.5150	$1,141.52	$1,141.55	$1,141.50