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	$160.34	7.156%	$171.8139	$171.81	$171.80	$171.80
Purchase #2	$84.92	12.347%	$95.4051	$95.41	$95.40	$95.40
Purchase #3	$141.97	11.294%	$158.0041	$158.00	$158.00	$158.00
Purchase #4	$52.38	13.824%	$59.621	$59.62	$59.60	$59.60
Purchase #5	$36.84	7.200%	$39.4925	$39.49	$39.50	$39.50
Purchase #6	$118.27	11.167%	$131.4772	$131.48	$131.50	$131.50
Purchase #7	$196.38	4.804%	$205.8141	$205.81	$205.80	$205.80
7 purchase totals =	$791.10		$861.6279	$861.62	$861.60	$861.60