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	$190.52	12.688%	$214.6932	$214.69	$214.70	$214.70
Purchase #2	$92.31	3.544%	$95.5815	$95.58	$95.60	$95.60
Purchase #3	$80.50	13.379%	$91.2701	$91.27	$91.25	$91.30
Purchase #4	$180.88	10.190%	$199.3117	$199.31	$199.30	$199.30
Purchase #5	$229.80	13.278%	$260.3128	$260.31	$260.30	$260.30
Purchase #6	$249.33	4.627%	$260.8665	$260.87	$260.85	$260.90
Purchase #7	$123.60	3.470%	$127.8889	$127.89	$127.90	$127.90
7 purchase totals =	$1,146.94		$1,249.9247	$1,249.92	$1,249.90	$1,250.00