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	$127.92	13.278%	$144.9052	$144.91	$144.90	$144.90
Purchase #2	$229.46	4.861%	$240.6141	$240.61	$240.60	$240.60
Purchase #3	$100.52	8.838%	$109.404	$109.40	$109.40	$109.40
Purchase #4	$243.74	7.357%	$261.672	$261.67	$261.65	$261.70
Purchase #5	$89.75	5.598%	$94.7742	$94.77	$94.75	$94.80
Purchase #6	$224.73	7.365%	$241.2814	$241.28	$241.30	$241.30
Purchase #7	$58.94	13.791%	$67.0684	$67.07	$67.05	$67.10
7 purchase totals =	$1,075.06		$1,159.7193	$1,159.71	$1,159.65	$1,159.80