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	$17.47	5.737%	$18.4723	$18.47	$18.45	$18.50
Purchase #2	$239.91	6.615%	$255.78	$255.78	$255.80	$255.80
Purchase #3	$103.63	5.813%	$109.654	$109.65	$109.65	$109.70
Purchase #4	$146.66	7.468%	$157.6126	$157.61	$157.60	$157.60
Purchase #5	$77.93	8.176%	$84.3016	$84.30	$84.30	$84.30
Purchase #6	$171.32	7.744%	$184.587	$184.59	$184.60	$184.60
Purchase #7	$189.72	5.175%	$199.538	$199.54	$199.55	$199.50
7 purchase totals =	$946.64		$1,009.9455	$1,009.94	$1,009.95	$1,010.00