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	$218.32	5.774%	$230.9258	$230.93	$230.95	$230.90
Purchase #2	$45.76	6.366%	$48.6731	$48.67	$48.65	$48.70
Purchase #3	$127.83	9.367%	$139.8038	$139.80	$139.80	$139.80
Purchase #4	$239.65	7.774%	$258.2804	$258.28	$258.30	$258.30
Purchase #5	$87.78	13.714%	$99.8181	$99.82	$99.80	$99.80
Purchase #6	$142.85	5.818%	$151.161	$151.16	$151.15	$151.20
Purchase #7	$220.91	4.796%	$231.5048	$231.50	$231.50	$231.50
7 purchase totals =	$1,083.10		$1,160.1670	$1,160.16	$1,160.15	$1,160.20