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	$163.66	9.331%	$178.9311	$178.93	$178.95	$178.90
Purchase #2	$70.30	12.197%	$78.8745	$78.87	$78.85	$78.90
Purchase #3	$125.45	9.337%	$137.1633	$137.16	$137.15	$137.20
Purchase #4	$77.44	6.804%	$82.709	$82.71	$82.70	$82.70
Purchase #5	$153.92	11.112%	$171.0236	$171.02	$171.00	$171.00
Purchase #6	$107.83	5.593%	$113.8609	$113.86	$113.85	$113.90
Purchase #7	$52.92	11.349%	$58.9259	$58.93	$58.95	$58.90
7 purchase totals =	$751.52		$821.4883	$821.48	$821.45	$821.50