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	$52.86	4.355%	$55.1621	$55.16	$55.15	$55.20
Purchase #2	$132.82	3.179%	$137.0423	$137.04	$137.05	$137.00
Purchase #3	$63.87	13.639%	$72.5812	$72.58	$72.60	$72.60
Purchase #4	$154.67	12.427%	$173.8908	$173.89	$173.90	$173.90
Purchase #5	$74.62	4.460%	$77.9481	$77.95	$77.95	$77.90
Purchase #6	$14.76	3.107%	$15.2186	$15.22	$15.20	$15.20
Purchase #7	$163.26	5.697%	$172.5609	$172.56	$172.55	$172.60
7 purchase totals =	$656.86		$704.4040	$704.40	$704.40	$704.40