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	$98.93	9.548%	$108.3758	$108.38	$108.40	$108.40
Purchase #2	$12.82	5.447%	$13.5183	$13.52	$13.50	$13.50
Purchase #3	$73.93	11.512%	$82.4408	$82.44	$82.45	$82.40
Purchase #4	$139.48	9.409%	$152.6037	$152.60	$152.60	$152.60
Purchase #5	$154.71	6.139%	$164.2076	$164.21	$164.20	$164.20
Purchase #6	$53.96	10.542%	$59.6485	$59.65	$59.65	$59.60
Purchase #7	$176.30	4.616%	$184.438	$184.44	$184.45	$184.40
7 purchase totals =	$710.13		$765.2327	$765.24	$765.25	$765.10