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	$210.41	12.549%	$236.8144	$236.81	$236.80	$236.80
Purchase #2	$84.98	4.734%	$89.003	$89.00	$89.00	$89.00
Purchase #3	$28.49	9.211%	$31.1142	$31.11	$31.10	$31.10
Purchase #4	$199.73	4.575%	$208.8676	$208.87	$208.85	$208.90
Purchase #5	$152.56	13.584%	$173.2838	$173.28	$173.30	$173.30
Purchase #6	$155.57	11.723%	$173.8075	$173.81	$173.80	$173.80
Purchase #7	$140.82	13.291%	$159.5364	$159.54	$159.55	$159.50
7 purchase totals =	$972.56		$1,072.4269	$1,072.42	$1,072.40	$1,072.40