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	$140.38	3.803%	$145.7187	$145.72	$145.70	$145.70
Purchase #2	$167.70	12.265%	$188.2684	$188.27	$188.25	$188.30
Purchase #3	$132.37	7.685%	$142.5426	$142.54	$142.55	$142.50
Purchase #4	$240.82	5.186%	$253.3089	$253.31	$253.30	$253.30
Purchase #5	$153.77	13.726%	$174.8765	$174.88	$174.90	$174.90
Purchase #6	$228.85	5.834%	$242.2011	$242.20	$242.20	$242.20
Purchase #7	$38.27	6.660%	$40.8188	$40.82	$40.80	$40.80
7 purchase totals =	$1,102.16		$1,187.7350	$1,187.74	$1,187.70	$1,187.70