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	$105.43	7.695%	$113.5428	$113.54	$113.55	$113.50
Purchase #2	$236.93	3.326%	$244.8103	$244.81	$244.80	$244.80
Purchase #3	$103.53	5.574%	$109.3008	$109.30	$109.30	$109.30
Purchase #4	$63.37	13.545%	$71.9535	$71.95	$71.95	$72.00
Purchase #5	$107.66	4.671%	$112.6888	$112.69	$112.70	$112.70
Purchase #6	$94.57	11.619%	$105.5581	$105.56	$105.55	$105.60
Purchase #7	$124.54	13.549%	$141.4139	$141.41	$141.40	$141.40
7 purchase totals =	$836.03		$899.2682	$899.26	$899.25	$899.30