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	$54.97	5.422%	$57.9505	$57.95	$57.95	$58.00
Purchase #2	$57.69	3.352%	$59.6238	$59.62	$59.60	$59.60
Purchase #3	$178.41	12.114%	$200.0226	$200.02	$200.00	$200.00
Purchase #4	$189.72	3.581%	$196.5139	$196.51	$196.50	$196.50
Purchase #5	$86.86	4.466%	$90.7392	$90.74	$90.75	$90.70
Purchase #6	$126.30	7.769%	$136.1122	$136.11	$136.10	$136.10
Purchase #7	$10.81	3.758%	$11.2162	$11.22	$11.20	$11.20
7 purchase totals =	$704.76		$752.1784	$752.17	$752.10	$752.10