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	$102.67	13.420%	$116.4483	$116.45	$116.45	$116.40
Purchase #2	$34.69	13.226%	$39.2781	$39.28	$39.30	$39.30
Purchase #3	$179.79	12.109%	$201.5608	$201.56	$201.55	$201.60
Purchase #4	$39.45	3.723%	$40.9187	$40.92	$40.90	$40.90
Purchase #5	$30.60	7.317%	$32.839	$32.84	$32.85	$32.80
Purchase #6	$171.34	8.234%	$185.4481	$185.45	$185.45	$185.40
Purchase #7	$133.52	6.190%	$141.7849	$141.78	$141.80	$141.80
7 purchase totals =	$692.06		$758.2779	$758.28	$758.30	$758.20