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	$184.29	6.687%	$196.6135	$196.61	$196.60	$196.60
Purchase #2	$72.85	9.379%	$79.6826	$79.68	$79.70	$79.70
Purchase #3	$167.77	12.422%	$188.6104	$188.61	$188.60	$188.60
Purchase #4	$17.75	10.401%	$19.5962	$19.60	$19.60	$19.60
Purchase #5	$85.34	6.346%	$90.7557	$90.76	$90.75	$90.80
Purchase #6	$249.37	4.791%	$261.3173	$261.32	$261.30	$261.30
Purchase #7	$68.63	4.167%	$71.4898	$71.49	$71.50	$71.50
7 purchase totals =	$846.00		$908.0655	$908.07	$908.05	$908.10