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	$197.63	11.594%	$220.5432	$220.54	$220.55	$220.50
Purchase #2	$77.92	8.488%	$84.5338	$84.53	$84.55	$84.50
Purchase #3	$34.26	3.607%	$35.4958	$35.50	$35.50	$35.50
Purchase #4	$87.73	4.196%	$91.4112	$91.41	$91.40	$91.40
Purchase #5	$123.31	3.491%	$127.6148	$127.61	$127.60	$127.60
Purchase #6	$162.82	13.520%	$184.8333	$184.83	$184.85	$184.80
Purchase #7	$229.55	3.846%	$238.3785	$238.38	$238.40	$238.40
7 purchase totals =	$913.22		$982.8106	$982.80	$982.85	$982.70