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	$176.78	8.782%	$192.3048	$192.30	$192.30	$192.30
Purchase #2	$117.52	8.271%	$127.2401	$127.24	$127.25	$127.20
Purchase #3	$111.90	11.258%	$124.4977	$124.50	$124.50	$124.50
Purchase #4	$136.44	13.799%	$155.2674	$155.27	$155.25	$155.30
Purchase #5	$197.40	7.223%	$211.6582	$211.66	$211.65	$211.70
Purchase #6	$35.32	7.258%	$37.8835	$37.88	$37.90	$37.90
Purchase #7	$92.27	11.163%	$102.5701	$102.57	$102.55	$102.60
7 purchase totals =	$867.63		$951.4218	$951.42	$951.40	$951.50