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	$181.71	10.491%	$200.7732	$200.77	$200.75	$200.80
Purchase #2	$61.90	9.627%	$67.8591	$67.86	$67.85	$67.90
Purchase #3	$115.25	13.869%	$131.234	$131.23	$131.25	$131.20
Purchase #4	$100.38	8.308%	$108.7196	$108.72	$108.70	$108.70
Purchase #5	$68.25	3.774%	$70.8258	$70.83	$70.85	$70.80
Purchase #6	$231.69	3.131%	$238.9442	$238.94	$238.95	$238.90
Purchase #7	$71.87	9.731%	$78.8637	$78.86	$78.85	$78.90
7 purchase totals =	$831.05		$897.2196	$897.21	$897.20	$897.20