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	$153.29	9.107%	$167.2501	$167.25	$167.25	$167.30
Purchase #2	$59.39	3.849%	$61.6759	$61.68	$61.70	$61.70
Purchase #3	$61.53	10.238%	$67.8294	$67.83	$67.85	$67.80
Purchase #4	$125.72	12.865%	$141.8939	$141.89	$141.90	$141.90
Purchase #5	$68.97	10.326%	$76.0918	$76.09	$76.10	$76.10
Purchase #6	$123.66	10.315%	$136.4155	$136.42	$136.40	$136.40
Purchase #7	$229.60	13.416%	$260.4031	$260.40	$260.40	$260.40
7 purchase totals =	$822.16		$911.5597	$911.56	$911.60	$911.60