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	$9.71	9.272%	$10.6103	$10.61	$10.60	$10.60
Purchase #2	$121.73	12.822%	$137.3382	$137.34	$137.35	$137.30
Purchase #3	$18.87	4.501%	$19.7193	$19.72	$19.70	$19.70
Purchase #4	$70.83	13.662%	$80.5068	$80.51	$80.50	$80.50
Purchase #5	$179.64	7.240%	$192.6459	$192.65	$192.65	$192.60
Purchase #6	$190.33	3.433%	$196.864	$196.86	$196.85	$196.90
Purchase #7	$93.79	4.768%	$98.2619	$98.26	$98.25	$98.30
7 purchase totals =	$684.90		$735.9464	$735.95	$735.90	$735.90