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	$204.31	11.253%	$227.301	$227.30	$227.30	$227.30
Purchase #2	$49.97	8.231%	$54.083	$54.08	$54.10	$54.10
Purchase #3	$100.66	3.547%	$104.2304	$104.23	$104.25	$104.20
Purchase #4	$90.28	13.382%	$102.3613	$102.36	$102.35	$102.40
Purchase #5	$205.93	6.110%	$218.5123	$218.51	$218.50	$218.50
Purchase #6	$81.41	13.577%	$92.463	$92.46	$92.45	$92.50
Purchase #7	$50.39	10.205%	$55.5323	$55.53	$55.55	$55.50
7 purchase totals =	$782.95		$854.4833	$854.47	$854.50	$854.50