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	$9.76	8.736%	$10.6126	$10.61	$10.60	$10.60
Purchase #2	$61.44	3.757%	$63.7483	$63.75	$63.75	$63.70
Purchase #3	$100.74	11.647%	$112.4732	$112.47	$112.45	$112.50
Purchase #4	$221.49	5.592%	$233.8757	$233.88	$233.90	$233.90
Purchase #5	$240.59	5.867%	$254.7054	$254.71	$254.70	$254.70
Purchase #6	$53.74	11.203%	$59.7605	$59.76	$59.75	$59.80
Purchase #7	$38.76	3.619%	$40.1627	$40.16	$40.15	$40.20
7 purchase totals =	$726.52		$775.3384	$775.34	$775.30	$775.40