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	$102.59	10.190%	$113.0439	$113.04	$113.05	$113.00
Purchase #2	$156.40	9.565%	$171.3597	$171.36	$171.35	$171.40
Purchase #3	$246.75	3.756%	$256.0179	$256.02	$256.00	$256.00
Purchase #4	$97.35	8.537%	$105.6608	$105.66	$105.65	$105.70
Purchase #5	$38.89	11.709%	$43.4436	$43.44	$43.45	$43.40
Purchase #6	$129.54	10.233%	$142.7958	$142.80	$142.80	$142.80
Purchase #7	$61.73	8.762%	$67.1388	$67.14	$67.15	$67.10
7 purchase totals =	$833.25		$899.4605	$899.46	$899.45	$899.40