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	$221.78	7.139%	$237.6129	$237.61	$237.60	$237.60
Purchase #2	$85.30	4.779%	$89.3765	$89.38	$89.40	$89.40
Purchase #3	$36.84	4.247%	$38.4046	$38.40	$38.40	$38.40
Purchase #4	$242.53	8.546%	$263.2566	$263.26	$263.25	$263.30
Purchase #5	$146.94	13.499%	$166.7754	$166.78	$166.80	$166.80
Purchase #6	$158.25	9.233%	$172.8612	$172.86	$172.85	$172.90
Purchase #7	$37.61	11.602%	$41.9735	$41.97	$41.95	$42.00
7 purchase totals =	$929.25		$1,010.2607	$1,010.26	$1,010.25	$1,010.40