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	$216.50	3.273%	$223.586	$223.59	$223.60	$223.60
Purchase #2	$123.32	10.845%	$136.6941	$136.69	$136.70	$136.70
Purchase #3	$179.44	11.620%	$200.2909	$200.29	$200.30	$200.30
Purchase #4	$146.96	3.424%	$151.9919	$151.99	$152.00	$152.00
Purchase #5	$50.96	9.857%	$55.9831	$55.98	$56.00	$56.00
Purchase #6	$159.51	3.704%	$165.4183	$165.42	$165.40	$165.40
Purchase #7	$11.67	7.760%	$12.5756	$12.58	$12.60	$12.60
7 purchase totals =	$888.36		$946.5399	$946.54	$946.60	$946.60