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	$41.26	5.306%	$43.4493	$43.45	$43.45	$43.40
Purchase #2	$219.97	6.575%	$234.433	$234.43	$234.45	$234.40
Purchase #3	$30.99	3.477%	$32.0675	$32.07	$32.05	$32.10
Purchase #4	$84.95	6.785%	$90.7139	$90.71	$90.70	$90.70
Purchase #5	$36.84	9.421%	$40.3107	$40.31	$40.30	$40.30
Purchase #6	$69.50	4.459%	$72.599	$72.60	$72.60	$72.60
Purchase #7	$84.64	11.472%	$94.3499	$94.35	$94.35	$94.30
7 purchase totals =	$568.15		$607.9233	$607.92	$607.90	$607.80