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	$130.58	9.723%	$143.2763	$143.28	$143.30	$143.30
Purchase #2	$175.71	7.720%	$189.2748	$189.27	$189.25	$189.30
Purchase #3	$11.74	5.784%	$12.419	$12.42	$12.40	$12.40
Purchase #4	$155.42	8.712%	$168.9602	$168.96	$168.95	$169.00
Purchase #5	$166.77	13.744%	$189.6909	$189.69	$189.70	$189.70
Purchase #6	$35.82	4.179%	$37.3169	$37.32	$37.30	$37.30
Purchase #7	$250.65	4.288%	$261.3979	$261.40	$261.40	$261.40
7 purchase totals =	$926.69		$1,002.3360	$1,002.34	$1,002.30	$1,002.40