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	$9.96	3.393%	$10.2979	$10.30	$10.30	$10.30
Purchase #2	$38.90	10.594%	$43.0211	$43.02	$43.00	$43.00
Purchase #3	$213.54	4.369%	$222.8696	$222.87	$222.85	$222.90
Purchase #4	$113.41	4.356%	$118.3501	$118.35	$118.35	$118.40
Purchase #5	$66.56	5.858%	$70.4591	$70.46	$70.45	$70.50
Purchase #6	$119.79	13.386%	$135.8251	$135.83	$135.85	$135.80
Purchase #7	$13.66	6.331%	$14.5248	$14.52	$14.50	$14.50
7 purchase totals =	$575.82		$615.3477	$615.35	$615.30	$615.40