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	$236.33	12.483%	$265.8311	$265.83	$265.85	$265.80
Purchase #2	$164.33	4.403%	$171.5654	$171.57	$171.55	$171.60
Purchase #3	$104.60	8.633%	$113.6301	$113.63	$113.65	$113.60
Purchase #4	$54.81	9.242%	$59.8755	$59.88	$59.90	$59.90
Purchase #5	$15.72	7.569%	$16.9098	$16.91	$16.90	$16.90
Purchase #6	$200.79	8.293%	$217.4415	$217.44	$217.45	$217.40
Purchase #7	$217.58	4.447%	$227.2558	$227.26	$227.25	$227.30
7 purchase totals =	$994.16		$1,072.5092	$1,072.52	$1,072.55	$1,072.50