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	$115.72	9.757%	$127.0108	$127.01	$127.00	$127.00
Purchase #2	$165.56	8.189%	$179.1177	$179.12	$179.10	$179.10
Purchase #3	$104.67	9.483%	$114.5959	$114.60	$114.60	$114.60
Purchase #4	$156.58	7.624%	$168.5177	$168.52	$168.50	$168.50
Purchase #5	$248.26	8.123%	$268.4262	$268.43	$268.45	$268.40
Purchase #6	$41.32	10.170%	$45.5222	$45.52	$45.50	$45.50
Purchase #7	$244.95	7.351%	$262.9563	$262.96	$262.95	$263.00
7 purchase totals =	$1,077.06		$1,166.1468	$1,166.16	$1,166.10	$1,166.10