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	$91.67	5.315%	$96.5423	$96.54	$96.55	$96.50
Purchase #2	$114.28	11.861%	$127.8348	$127.83	$127.85	$127.80
Purchase #3	$190.28	8.181%	$205.8468	$205.85	$205.85	$205.80
Purchase #4	$40.27	5.358%	$42.4277	$42.43	$42.45	$42.40
Purchase #5	$226.99	5.282%	$238.9796	$238.98	$239.00	$239.00
Purchase #6	$168.43	10.621%	$186.319	$186.32	$186.30	$186.30
Purchase #7	$172.99	4.111%	$180.1016	$180.10	$180.10	$180.10
7 purchase totals =	$1,004.91		$1,078.0518	$1,078.05	$1,078.10	$1,077.90