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	$54.55	4.319%	$56.906	$56.91	$56.90	$56.90
Purchase #2	$151.46	8.662%	$164.5795	$164.58	$164.60	$164.60
Purchase #3	$144.63	9.209%	$157.949	$157.95	$157.95	$157.90
Purchase #4	$190.28	5.166%	$200.1099	$200.11	$200.10	$200.10
Purchase #5	$224.98	4.259%	$234.5619	$234.56	$234.55	$234.60
Purchase #6	$232.72	12.525%	$261.8682	$261.87	$261.85	$261.90
Purchase #7	$55.38	11.785%	$61.9065	$61.91	$61.90	$61.90
7 purchase totals =	$1,054.00		$1,137.8810	$1,137.89	$1,137.85	$1,137.90