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	$143.43	6.190%	$152.3083	$152.31	$152.30	$152.30
Purchase #2	$11.49	5.351%	$12.1048	$12.10	$12.10	$12.10
Purchase #3	$100.66	7.243%	$107.9508	$107.95	$107.95	$108.00
Purchase #4	$138.69	13.586%	$157.5324	$157.53	$157.55	$157.50
Purchase #5	$181.50	10.130%	$199.886	$199.89	$199.90	$199.90
Purchase #6	$109.92	12.394%	$123.5435	$123.54	$123.55	$123.50
Purchase #7	$108.91	7.706%	$117.3026	$117.30	$117.30	$117.30
7 purchase totals =	$794.60		$870.6284	$870.62	$870.65	$870.60