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	$138.70	5.363%	$146.1385	$146.14	$146.15	$146.10
Purchase #2	$78.30	4.599%	$81.901	$81.90	$81.90	$81.90
Purchase #3	$177.92	11.687%	$198.7135	$198.71	$198.70	$198.70
Purchase #4	$34.59	7.419%	$37.1562	$37.16	$37.15	$37.20
Purchase #5	$52.40	12.403%	$58.8992	$58.90	$58.90	$58.90
Purchase #6	$156.83	7.582%	$168.7209	$168.72	$168.70	$168.70
Purchase #7	$12.85	3.306%	$13.2748	$13.27	$13.25	$13.30
7 purchase totals =	$651.59		$704.8041	$704.80	$704.75	$704.80