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	$183.72	11.323%	$204.5226	$204.52	$204.50	$204.50
Purchase #2	$192.88	10.693%	$213.5047	$213.50	$213.50	$213.50
Purchase #3	$12.90	11.288%	$14.3562	$14.36	$14.35	$14.40
Purchase #4	$47.81	4.798%	$50.1039	$50.10	$50.10	$50.10
Purchase #5	$128.80	12.147%	$144.4453	$144.45	$144.45	$144.40
Purchase #6	$227.41	12.766%	$256.4412	$256.44	$256.45	$256.40
Purchase #7	$26.81	11.472%	$29.8856	$29.89	$29.90	$29.90
7 purchase totals =	$820.33		$913.2595	$913.26	$913.25	$913.20