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	$64.52	5.187%	$67.8667	$67.87	$67.85	$67.90
Purchase #2	$21.25	4.141%	$22.13	$22.13	$22.15	$22.10
Purchase #3	$114.54	3.556%	$118.613	$118.61	$118.60	$118.60
Purchase #4	$102.91	5.447%	$108.5155	$108.52	$108.50	$108.50
Purchase #5	$78.49	4.840%	$82.2889	$82.29	$82.30	$82.30
Purchase #6	$83.30	13.278%	$94.3606	$94.36	$94.35	$94.40
Purchase #7	$65.66	7.280%	$70.44	$70.44	$70.45	$70.40
7 purchase totals =	$530.67		$564.2147	$564.22	$564.20	$564.20