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	$131.51	8.327%	$142.4608	$142.46	$142.45	$142.50
Purchase #2	$202.46	7.762%	$218.1749	$218.17	$218.15	$218.20
Purchase #3	$245.65	12.251%	$275.7446	$275.74	$275.75	$275.70
Purchase #4	$204.40	5.250%	$215.131	$215.13	$215.15	$215.10
Purchase #5	$16.60	4.184%	$17.2945	$17.29	$17.30	$17.30
Purchase #6	$184.27	3.273%	$190.3012	$190.30	$190.30	$190.30
Purchase #7	$131.43	9.820%	$144.3364	$144.34	$144.35	$144.30
7 purchase totals =	$1,116.32		$1,203.4434	$1,203.43	$1,203.45	$1,203.40