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	$33.97	10.233%	$37.4462	$37.45	$37.45	$37.40
Purchase #2	$49.92	11.398%	$55.6099	$55.61	$55.60	$55.60
Purchase #3	$85.78	12.277%	$96.3112	$96.31	$96.30	$96.30
Purchase #4	$31.88	5.784%	$33.7239	$33.72	$33.70	$33.70
Purchase #5	$229.43	8.211%	$248.2685	$248.27	$248.25	$248.30
Purchase #6	$152.89	3.380%	$158.0577	$158.06	$158.05	$158.10
Purchase #7	$209.66	9.609%	$229.8062	$229.81	$229.80	$229.80
7 purchase totals =	$793.53		$859.2236	$859.23	$859.15	$859.20