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	$107.52	4.249%	$112.0885	$112.09	$112.10	$112.10
Purchase #2	$196.25	7.710%	$211.3809	$211.38	$211.40	$211.40
Purchase #3	$150.84	4.676%	$157.8933	$157.89	$157.90	$157.90
Purchase #4	$167.55	3.641%	$173.6505	$173.65	$173.65	$173.70
Purchase #5	$69.34	4.614%	$72.5393	$72.54	$72.55	$72.50
Purchase #6	$164.25	7.324%	$176.2797	$176.28	$176.30	$176.30
Purchase #7	$39.39	9.435%	$43.1064	$43.11	$43.10	$43.10
7 purchase totals =	$895.14		$946.9386	$946.94	$947.00	$947.00