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	$91.67	9.748%	$100.606	$100.61	$100.60	$100.60
Purchase #2	$156.59	4.818%	$164.1345	$164.13	$164.15	$164.10
Purchase #3	$167.52	7.672%	$180.3721	$180.37	$180.35	$180.40
Purchase #4	$200.73	6.854%	$214.488	$214.49	$214.50	$214.50
Purchase #5	$102.88	4.515%	$107.525	$107.53	$107.55	$107.50
Purchase #6	$204.88	13.167%	$231.8565	$231.86	$231.85	$231.90
Purchase #7	$7.45	5.747%	$7.8782	$7.88	$7.90	$7.90
7 purchase totals =	$931.72		$1,006.8603	$1,006.87	$1,006.90	$1,006.90