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	$51.51	6.509%	$54.8628	$54.86	$54.85	$54.90
Purchase #2	$33.33	13.517%	$37.8352	$37.84	$37.85	$37.80
Purchase #3	$112.32	7.448%	$120.6856	$120.69	$120.70	$120.70
Purchase #4	$71.54	11.333%	$79.6476	$79.65	$79.65	$79.60
Purchase #5	$169.28	12.764%	$190.8869	$190.89	$190.90	$190.90
Purchase #6	$196.92	6.868%	$210.4445	$210.44	$210.45	$210.40
Purchase #7	$24.74	11.575%	$27.6037	$27.60	$27.60	$27.60
7 purchase totals =	$659.64		$721.9663	$721.97	$722.00	$721.90