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	$39.66	13.373%	$44.9637	$44.96	$44.95	$45.00
Purchase #2	$92.40	13.818%	$105.1678	$105.17	$105.15	$105.20
Purchase #3	$236.69	3.225%	$244.3233	$244.32	$244.30	$244.30
Purchase #4	$37.59	12.161%	$42.1613	$42.16	$42.15	$42.20
Purchase #5	$167.54	8.468%	$181.7273	$181.73	$181.75	$181.70
Purchase #6	$216.26	11.249%	$240.5871	$240.59	$240.60	$240.60
Purchase #7	$146.69	9.382%	$160.4525	$160.45	$160.45	$160.50
7 purchase totals =	$936.83		$1,019.3830	$1,019.38	$1,019.35	$1,019.50