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	$247.80	3.666%	$256.8843	$256.88	$256.90	$256.90
Purchase #2	$60.87	5.481%	$64.2063	$64.21	$64.20	$64.20
Purchase #3	$51.26	5.207%	$53.9291	$53.93	$53.95	$53.90
Purchase #4	$211.92	10.324%	$233.7986	$233.80	$233.80	$233.80
Purchase #5	$22.45	13.752%	$25.5373	$25.54	$25.55	$25.50
Purchase #6	$40.78	4.284%	$42.527	$42.53	$42.55	$42.50
Purchase #7	$105.60	13.274%	$119.6173	$119.62	$119.60	$119.60
7 purchase totals =	$740.68		$796.4999	$796.51	$796.55	$796.40