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	$72.48	7.688%	$78.0523	$78.05	$78.05	$78.10
Purchase #2	$50.93	4.176%	$53.0568	$53.06	$53.05	$53.10
Purchase #3	$204.66	7.256%	$219.5101	$219.51	$219.50	$219.50
Purchase #4	$150.69	11.480%	$167.9892	$167.99	$168.00	$168.00
Purchase #5	$189.25	13.558%	$214.9085	$214.91	$214.90	$214.90
Purchase #6	$119.42	7.282%	$128.1162	$128.12	$128.10	$128.10
Purchase #7	$94.37	7.724%	$101.6591	$101.66	$101.65	$101.70
7 purchase totals =	$881.80		$963.2922	$963.30	$963.25	$963.40