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	$55.53	7.423%	$59.652	$59.65	$59.65	$59.70
Purchase #2	$59.44	11.196%	$66.0949	$66.09	$66.10	$66.10
Purchase #3	$224.60	4.116%	$233.8445	$233.84	$233.85	$233.80
Purchase #4	$157.76	11.197%	$175.4244	$175.42	$175.40	$175.40
Purchase #5	$35.67	6.242%	$37.8965	$37.90	$37.90	$37.90
Purchase #6	$218.43	3.285%	$225.6054	$225.61	$225.60	$225.60
Purchase #7	$155.82	6.416%	$165.8174	$165.82	$165.80	$165.80
7 purchase totals =	$907.25		$964.3351	$964.33	$964.30	$964.30