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	$125.58	9.781%	$137.863	$137.86	$137.85	$137.90
Purchase #2	$75.32	13.722%	$85.6554	$85.66	$85.65	$85.70
Purchase #3	$106.97	10.662%	$118.3751	$118.38	$118.40	$118.40
Purchase #4	$121.93	3.828%	$126.5975	$126.60	$126.60	$126.60
Purchase #5	$68.55	6.164%	$72.7754	$72.78	$72.80	$72.80
Purchase #6	$22.89	6.453%	$24.3671	$24.37	$24.35	$24.40
Purchase #7	$33.54	5.506%	$35.3867	$35.39	$35.40	$35.40
7 purchase totals =	$554.78		$601.0202	$601.04	$601.05	$601.20