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	$207.44	7.439%	$222.8715	$222.87	$222.85	$222.90
Purchase #2	$175.89	4.762%	$184.2659	$184.27	$184.25	$184.30
Purchase #3	$29.65	12.427%	$33.3346	$33.33	$33.35	$33.30
Purchase #4	$62.95	3.402%	$65.0916	$65.09	$65.10	$65.10
Purchase #5	$21.76	11.158%	$24.188	$24.19	$24.20	$24.20
Purchase #6	$61.58	13.308%	$69.7751	$69.78	$69.80	$69.80
Purchase #7	$39.67	5.604%	$41.8931	$41.89	$41.90	$41.90
7 purchase totals =	$598.94		$641.4198	$641.42	$641.45	$641.50