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	$103.61	10.426%	$114.4124	$114.41	$114.40	$114.40
Purchase #2	$114.38	9.777%	$125.5629	$125.56	$125.55	$125.60
Purchase #3	$40.90	11.662%	$45.6698	$45.67	$45.65	$45.70
Purchase #4	$114.87	11.304%	$127.8549	$127.85	$127.85	$127.90
Purchase #5	$202.91	9.583%	$222.3549	$222.35	$222.35	$222.40
Purchase #6	$60.87	4.457%	$63.583	$63.58	$63.60	$63.60
Purchase #7	$32.53	9.541%	$35.6337	$35.63	$35.65	$35.60
7 purchase totals =	$670.07		$735.0716	$735.05	$735.05	$735.20