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	$116.56	4.252%	$121.5161	$121.52	$121.50	$121.50
Purchase #2	$111.67	13.137%	$126.3401	$126.34	$126.35	$126.30
Purchase #3	$212.72	4.276%	$221.8159	$221.82	$221.80	$221.80
Purchase #4	$75.77	6.343%	$80.5761	$80.58	$80.60	$80.60
Purchase #5	$113.46	8.698%	$123.3288	$123.33	$123.35	$123.30
Purchase #6	$129.84	6.575%	$138.377	$138.38	$138.40	$138.40
Purchase #7	$249.89	13.751%	$284.2524	$284.25	$284.25	$284.30
7 purchase totals =	$1,009.91		$1,096.2064	$1,096.22	$1,096.25	$1,096.20