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	$161.36	4.527%	$168.6648	$168.66	$168.65	$168.70
Purchase #2	$197.78	5.329%	$208.3197	$208.32	$208.30	$208.30
Purchase #3	$239.72	13.412%	$271.8712	$271.87	$271.85	$271.90
Purchase #4	$29.91	10.116%	$32.9357	$32.94	$32.95	$32.90
Purchase #5	$241.39	3.461%	$249.7445	$249.74	$249.75	$249.70
Purchase #6	$83.81	8.869%	$91.2431	$91.24	$91.25	$91.20
Purchase #7	$114.76	3.577%	$118.865	$118.87	$118.85	$118.90
7 purchase totals =	$1,068.73		$1,141.6440	$1,141.64	$1,141.60	$1,141.60