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	$127.92	10.348%	$141.1572	$141.16	$141.15	$141.20
Purchase #2	$82.80	4.221%	$86.295	$86.30	$86.30	$86.30
Purchase #3	$166.84	9.769%	$183.1386	$183.14	$183.15	$183.10
Purchase #4	$148.71	6.160%	$157.8705	$157.87	$157.85	$157.90
Purchase #5	$197.70	12.450%	$222.3137	$222.31	$222.30	$222.30
Purchase #6	$248.40	13.469%	$281.857	$281.86	$281.85	$281.90
Purchase #7	$78.37	6.386%	$83.3747	$83.37	$83.35	$83.40
7 purchase totals =	$1,050.74		$1,156.0067	$1,156.01	$1,155.95	$1,156.10