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	$124.79	5.305%	$131.4101	$131.41	$131.40	$131.40
Purchase #2	$38.75	4.536%	$40.5077	$40.51	$40.50	$40.50
Purchase #3	$239.79	12.398%	$269.5192	$269.52	$269.50	$269.50
Purchase #4	$127.46	12.496%	$143.3874	$143.39	$143.40	$143.40
Purchase #5	$181.44	10.227%	$199.9959	$200.00	$200.00	$200.00
Purchase #6	$229.68	10.266%	$253.2589	$253.26	$253.25	$253.30
Purchase #7	$108.44	3.351%	$112.0738	$112.07	$112.05	$112.10
7 purchase totals =	$1,050.35		$1,150.1530	$1,150.16	$1,150.10	$1,150.20