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	$190.27	13.140%	$215.2715	$215.27	$215.25	$215.30
Purchase #2	$149.82	9.448%	$163.975	$163.98	$164.00	$164.00
Purchase #3	$212.88	7.795%	$229.474	$229.47	$229.45	$229.50
Purchase #4	$158.31	11.420%	$176.389	$176.39	$176.40	$176.40
Purchase #5	$35.44	5.310%	$37.3219	$37.32	$37.30	$37.30
Purchase #6	$54.31	5.384%	$57.2341	$57.23	$57.25	$57.20
Purchase #7	$16.47	13.226%	$18.6483	$18.65	$18.65	$18.60
7 purchase totals =	$817.50		$898.3138	$898.31	$898.30	$898.30