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	$26.77	10.842%	$29.6724	$29.67	$29.65	$29.70
Purchase #2	$235.78	6.526%	$251.167	$251.17	$251.15	$251.20
Purchase #3	$31.89	10.714%	$35.3067	$35.31	$35.30	$35.30
Purchase #4	$87.82	10.164%	$96.746	$96.75	$96.75	$96.70
Purchase #5	$158.45	6.269%	$168.3832	$168.38	$168.40	$168.40
Purchase #6	$241.90	8.163%	$261.6463	$261.65	$261.65	$261.60
Purchase #7	$208.56	6.845%	$222.8359	$222.84	$222.85	$222.80
7 purchase totals =	$991.17		$1,065.7575	$1,065.77	$1,065.75	$1,065.70