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	$154.97	7.773%	$167.0158	$167.02	$167.00	$167.00
Purchase #2	$189.27	11.401%	$210.8487	$210.85	$210.85	$210.80
Purchase #3	$182.38	8.574%	$198.0173	$198.02	$198.00	$198.00
Purchase #4	$114.60	11.569%	$127.8581	$127.86	$127.85	$127.90
Purchase #5	$159.47	7.560%	$171.5259	$171.53	$171.55	$171.50
Purchase #6	$99.83	5.643%	$105.4634	$105.46	$105.45	$105.50
Purchase #7	$132.55	11.286%	$147.5096	$147.51	$147.50	$147.50
7 purchase totals =	$1,033.07		$1,128.2388	$1,128.25	$1,128.20	$1,128.20