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	$249.43	5.276%	$262.5899	$262.59	$262.60	$262.60
Purchase #2	$168.29	6.831%	$179.7859	$179.79	$179.80	$179.80
Purchase #3	$64.59	4.460%	$67.4707	$67.47	$67.45	$67.50
Purchase #4	$144.37	9.844%	$158.5818	$158.58	$158.60	$158.60
Purchase #5	$25.31	8.125%	$27.3664	$27.37	$27.35	$27.40
Purchase #6	$220.92	7.216%	$236.8616	$236.86	$236.85	$236.90
Purchase #7	$216.64	8.748%	$235.5917	$235.59	$235.60	$235.60
7 purchase totals =	$1,089.55		$1,168.2480	$1,168.25	$1,168.25	$1,168.40