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	$15.35	4.855%	$16.0952	$16.10	$16.10	$16.10
Purchase #2	$141.76	7.129%	$151.8661	$151.87	$151.85	$151.90
Purchase #3	$191.78	11.381%	$213.6065	$213.61	$213.60	$213.60
Purchase #4	$163.54	5.543%	$172.605	$172.61	$172.60	$172.60
Purchase #5	$123.66	4.627%	$129.3817	$129.38	$129.40	$129.40
Purchase #6	$141.42	6.786%	$151.0168	$151.02	$151.00	$151.00
Purchase #7	$204.65	10.825%	$226.8034	$226.80	$226.80	$226.80
7 purchase totals =	$982.16		$1,061.3747	$1,061.39	$1,061.35	$1,061.40