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	$41.33	12.874%	$46.6508	$46.65	$46.65	$46.70
Purchase #2	$232.59	4.153%	$242.2495	$242.25	$242.25	$242.20
Purchase #3	$59.44	8.478%	$64.4793	$64.48	$64.50	$64.50
Purchase #4	$118.45	4.531%	$123.817	$123.82	$123.80	$123.80
Purchase #5	$52.54	10.186%	$57.8917	$57.89	$57.90	$57.90
Purchase #6	$49.56	4.359%	$51.7203	$51.72	$51.70	$51.70
Purchase #7	$232.81	3.631%	$241.2633	$241.26	$241.25	$241.30
7 purchase totals =	$786.72		$828.0719	$828.07	$828.05	$828.10