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	$40.67	6.500%	$43.3136	$43.31	$43.30	$43.30
Purchase #2	$195.35	4.131%	$203.4199	$203.42	$203.40	$203.40
Purchase #3	$140.94	6.810%	$150.538	$150.54	$150.55	$150.50
Purchase #4	$156.80	10.660%	$173.5149	$173.51	$173.50	$173.50
Purchase #5	$158.53	9.273%	$173.2305	$173.23	$173.25	$173.20
Purchase #6	$132.44	11.365%	$147.4918	$147.49	$147.50	$147.50
Purchase #7	$135.86	11.553%	$151.5559	$151.56	$151.55	$151.60
7 purchase totals =	$960.59		$1,043.0646	$1,043.06	$1,043.05	$1,043.00