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	$57.93	4.494%	$60.5334	$60.53	$60.55	$60.50
Purchase #2	$55.71	6.221%	$59.1757	$59.18	$59.20	$59.20
Purchase #3	$184.58	5.225%	$194.2243	$194.22	$194.20	$194.20
Purchase #4	$87.25	5.761%	$92.2765	$92.28	$92.30	$92.30
Purchase #5	$46.63	11.377%	$51.9351	$51.94	$51.95	$51.90
Purchase #6	$211.51	13.599%	$240.2732	$240.27	$240.25	$240.30
Purchase #7	$31.28	7.559%	$33.6445	$33.64	$33.65	$33.60
7 purchase totals =	$674.89		$732.0627	$732.06	$732.10	$732.00