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	$168.89	6.378%	$179.6618	$179.66	$179.65	$179.70
Purchase #2	$60.66	6.791%	$64.7794	$64.78	$64.80	$64.80
Purchase #3	$158.59	13.831%	$180.5246	$180.52	$180.50	$180.50
Purchase #4	$198.47	8.302%	$214.947	$214.95	$214.95	$214.90
Purchase #5	$113.27	11.228%	$125.988	$125.99	$126.00	$126.00
Purchase #6	$94.40	12.106%	$105.8281	$105.83	$105.85	$105.80
Purchase #7	$245.47	11.121%	$272.7687	$272.77	$272.75	$272.80
7 purchase totals =	$1,039.75		$1,144.4976	$1,144.50	$1,144.50	$1,144.50