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	$159.84	3.434%	$165.3289	$165.33	$165.35	$165.30
Purchase #2	$145.51	13.772%	$165.5496	$165.55	$165.55	$165.50
Purchase #3	$159.27	3.250%	$164.4463	$164.45	$164.45	$164.40
Purchase #4	$176.36	10.159%	$194.2764	$194.28	$194.30	$194.30
Purchase #5	$151.44	7.376%	$162.6102	$162.61	$162.60	$162.60
Purchase #6	$244.35	7.379%	$262.3806	$262.38	$262.40	$262.40
Purchase #7	$80.62	6.161%	$85.587	$85.59	$85.60	$85.60
7 purchase totals =	$1,117.39		$1,200.1790	$1,200.19	$1,200.25	$1,200.10