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	$206.79	9.585%	$226.6108	$226.61	$226.60	$226.60
Purchase #2	$172.44	4.388%	$180.0067	$180.01	$180.00	$180.00
Purchase #3	$51.84	3.287%	$53.544	$53.54	$53.55	$53.50
Purchase #4	$55.74	6.359%	$59.2845	$59.28	$59.30	$59.30
Purchase #5	$168.87	12.268%	$189.587	$189.59	$189.60	$189.60
Purchase #6	$153.79	10.125%	$169.3612	$169.36	$169.35	$169.40
Purchase #7	$242.79	13.633%	$275.8896	$275.89	$275.90	$275.90
7 purchase totals =	$1,052.26		$1,154.2838	$1,154.28	$1,154.30	$1,154.30