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	$123.86	10.354%	$136.6845	$136.68	$136.70	$136.70
Purchase #2	$123.46	3.201%	$127.412	$127.41	$127.40	$127.40
Purchase #3	$249.68	10.268%	$275.3171	$275.32	$275.30	$275.30
Purchase #4	$99.40	3.585%	$102.9635	$102.96	$102.95	$103.00
Purchase #5	$225.88	13.289%	$255.8972	$255.90	$255.90	$255.90
Purchase #6	$156.86	4.874%	$164.5054	$164.51	$164.50	$164.50
Purchase #7	$115.26	3.611%	$119.422	$119.42	$119.40	$119.40
7 purchase totals =	$1,094.40		$1,182.2017	$1,182.20	$1,182.15	$1,182.20