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	$174.99	12.235%	$196.4	$196.40	$196.40	$196.40
Purchase #2	$180.27	6.777%	$192.4869	$192.49	$192.50	$192.50
Purchase #3	$105.60	13.178%	$119.516	$119.52	$119.50	$119.50
Purchase #4	$214.26	13.737%	$243.6929	$243.69	$243.70	$243.70
Purchase #5	$85.93	11.157%	$95.5172	$95.52	$95.50	$95.50
Purchase #6	$168.93	6.266%	$179.5152	$179.52	$179.50	$179.50
Purchase #7	$86.60	7.171%	$92.8101	$92.81	$92.80	$92.80
7 purchase totals =	$1,016.58		$1,119.9383	$1,119.95	$1,119.90	$1,119.90