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	$155.46	10.855%	$172.3352	$172.34	$172.35	$172.30
Purchase #2	$240.87	7.870%	$259.8265	$259.83	$259.85	$259.80
Purchase #3	$48.93	13.322%	$55.4485	$55.45	$55.45	$55.40
Purchase #4	$39.48	12.519%	$44.4225	$44.42	$44.40	$44.40
Purchase #5	$149.32	11.686%	$166.7695	$166.77	$166.75	$166.80
Purchase #6	$183.98	3.631%	$190.6603	$190.66	$190.65	$190.70
Purchase #7	$131.90	3.657%	$136.7236	$136.72	$136.70	$136.70
7 purchase totals =	$949.94		$1,026.1861	$1,026.19	$1,026.15	$1,026.10