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	$208.77	6.686%	$222.7284	$222.73	$222.75	$222.70
Purchase #2	$84.33	8.342%	$91.3648	$91.36	$91.35	$91.40
Purchase #3	$223.81	6.708%	$238.8232	$238.82	$238.80	$238.80
Purchase #4	$76.91	13.142%	$87.0175	$87.02	$87.00	$87.00
Purchase #5	$59.77	3.851%	$62.0717	$62.07	$62.05	$62.10
Purchase #6	$111.69	11.566%	$124.6081	$124.61	$124.60	$124.60
Purchase #7	$164.51	8.564%	$178.5986	$178.60	$178.60	$178.60
7 purchase totals =	$929.79		$1,005.2123	$1,005.21	$1,005.15	$1,005.20