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	$88.52	7.169%	$94.866	$94.87	$94.85	$94.90
Purchase #2	$35.93	3.135%	$37.0564	$37.06	$37.05	$37.10
Purchase #3	$113.82	11.814%	$127.2667	$127.27	$127.25	$127.30
Purchase #4	$71.89	13.228%	$81.3996	$81.40	$81.40	$81.40
Purchase #5	$217.97	13.274%	$246.9033	$246.90	$246.90	$246.90
Purchase #6	$38.79	10.400%	$42.8242	$42.82	$42.80	$42.80
Purchase #7	$43.86	11.271%	$48.8035	$48.80	$48.80	$48.80
7 purchase totals =	$610.78		$679.1197	$679.12	$679.05	$679.20