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	$60.48	5.424%	$63.7604	$63.76	$63.75	$63.80
Purchase #2	$192.66	12.420%	$216.5884	$216.59	$216.60	$216.60
Purchase #3	$39.66	4.658%	$41.5074	$41.51	$41.50	$41.50
Purchase #4	$238.94	6.225%	$253.814	$253.81	$253.80	$253.80
Purchase #5	$10.77	7.496%	$11.5773	$11.58	$11.60	$11.60
Purchase #6	$99.59	3.815%	$103.3894	$103.39	$103.40	$103.40
Purchase #7	$17.89	5.522%	$18.8779	$18.88	$18.90	$18.90
7 purchase totals =	$659.99		$709.5148	$709.52	$709.55	$709.60