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	$214.55	13.252%	$242.9822	$242.98	$243.00	$243.00
Purchase #2	$168.37	6.322%	$179.0144	$179.01	$179.00	$179.00
Purchase #3	$148.72	5.242%	$156.5159	$156.52	$156.50	$156.50
Purchase #4	$132.77	9.674%	$145.6142	$145.61	$145.60	$145.60
Purchase #5	$173.33	10.249%	$191.0946	$191.09	$191.10	$191.10
Purchase #6	$96.36	3.269%	$99.51	$99.51	$99.50	$99.50
Purchase #7	$6.92	12.586%	$7.791	$7.79	$7.80	$7.80
7 purchase totals =	$941.02		$1,022.5223	$1,022.51	$1,022.50	$1,022.50