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	$14.34	6.584%	$15.2841	$15.28	$15.30	$15.30
Purchase #2	$131.84	11.561%	$147.082	$147.08	$147.10	$147.10
Purchase #3	$117.47	6.126%	$124.6662	$124.67	$124.65	$124.70
Purchase #4	$160.81	3.852%	$167.0044	$167.00	$167.00	$167.00
Purchase #5	$234.51	9.358%	$256.4554	$256.46	$256.45	$256.50
Purchase #6	$236.85	11.582%	$264.282	$264.28	$264.30	$264.30
Purchase #7	$106.57	4.262%	$111.112	$111.11	$111.10	$111.10
7 purchase totals =	$1,002.39		$1,085.8861	$1,085.88	$1,085.90	$1,086.00