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	$172.86	3.822%	$179.4667	$179.47	$179.45	$179.50
Purchase #2	$134.46	5.849%	$142.3246	$142.32	$142.30	$142.30
Purchase #3	$136.76	3.325%	$141.3073	$141.31	$141.30	$141.30
Purchase #4	$5.49	3.870%	$5.7025	$5.70	$5.70	$5.70
Purchase #5	$114.96	3.196%	$118.6341	$118.63	$118.65	$118.60
Purchase #6	$185.81	9.499%	$203.4601	$203.46	$203.45	$203.50
Purchase #7	$10.83	10.124%	$11.9264	$11.93	$11.95	$11.90
7 purchase totals =	$761.17		$802.8217	$802.82	$802.80	$802.80