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	$127.49	4.765%	$133.5649	$133.56	$133.55	$133.60
Purchase #2	$169.53	9.493%	$185.6235	$185.62	$185.60	$185.60
Purchase #3	$53.93	6.646%	$57.5142	$57.51	$57.50	$57.50
Purchase #4	$210.69	13.715%	$239.5861	$239.59	$239.60	$239.60
Purchase #5	$166.62	12.148%	$186.861	$186.86	$186.85	$186.90
Purchase #6	$117.37	8.841%	$127.7467	$127.75	$127.75	$127.70
Purchase #7	$206.78	13.674%	$235.0551	$235.06	$235.05	$235.10
7 purchase totals =	$1,052.41		$1,165.9515	$1,165.95	$1,165.90	$1,166.00