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	$77.55	9.150%	$84.6458	$84.65	$84.65	$84.60
Purchase #2	$30.93	13.789%	$35.1949	$35.19	$35.20	$35.20
Purchase #3	$123.48	3.543%	$127.8549	$127.85	$127.85	$127.90
Purchase #4	$174.61	4.741%	$182.8883	$182.89	$182.90	$182.90
Purchase #5	$25.94	6.228%	$27.5555	$27.56	$27.55	$27.60
Purchase #6	$84.92	8.845%	$92.4312	$92.43	$92.45	$92.40
Purchase #7	$189.73	11.676%	$211.8829	$211.88	$211.90	$211.90
7 purchase totals =	$707.16		$762.4535	$762.45	$762.50	$762.50