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	$73.46	5.703%	$77.6494	$77.65	$77.65	$77.60
Purchase #2	$190.84	7.201%	$204.5824	$204.58	$204.60	$204.60
Purchase #3	$61.31	8.702%	$66.6452	$66.65	$66.65	$66.60
Purchase #4	$178.56	4.239%	$186.1292	$186.13	$186.15	$186.10
Purchase #5	$89.90	11.198%	$99.967	$99.97	$99.95	$100.00
Purchase #6	$71.66	9.705%	$78.6146	$78.61	$78.60	$78.60
Purchase #7	$19.98	9.147%	$21.8076	$21.81	$21.80	$21.80
7 purchase totals =	$685.71		$735.3954	$735.40	$735.40	$735.30