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	$237.87	11.126%	$264.3354	$264.34	$264.35	$264.30
Purchase #2	$101.98	9.480%	$111.6477	$111.65	$111.65	$111.60
Purchase #3	$131.25	7.721%	$141.3838	$141.38	$141.40	$141.40
Purchase #4	$120.73	8.561%	$131.0657	$131.07	$131.05	$131.10
Purchase #5	$59.98	10.465%	$66.2569	$66.26	$66.25	$66.30
Purchase #6	$119.71	11.668%	$133.6778	$133.68	$133.70	$133.70
Purchase #7	$156.97	10.354%	$173.2227	$173.22	$173.20	$173.20
7 purchase totals =	$928.49		$1,021.5900	$1,021.60	$1,021.60	$1,021.60