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	$173.41	9.611%	$190.0764	$190.08	$190.10	$190.10
Purchase #2	$172.30	3.784%	$178.8198	$178.82	$178.80	$178.80
Purchase #3	$49.98	5.816%	$52.8868	$52.89	$52.90	$52.90
Purchase #4	$248.82	5.162%	$261.6641	$261.66	$261.65	$261.70
Purchase #5	$52.38	11.226%	$58.2602	$58.26	$58.25	$58.30
Purchase #6	$19.79	13.682%	$22.4977	$22.50	$22.50	$22.50
Purchase #7	$17.79	13.824%	$20.2493	$20.25	$20.25	$20.20
7 purchase totals =	$734.47		$784.4543	$784.46	$784.45	$784.50