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	$102.42	8.708%	$111.3387	$111.34	$111.35	$111.30
Purchase #2	$133.91	13.649%	$152.1874	$152.19	$152.20	$152.20
Purchase #3	$198.45	12.826%	$223.9032	$223.90	$223.90	$223.90
Purchase #4	$117.96	13.123%	$133.4399	$133.44	$133.45	$133.40
Purchase #5	$35.36	13.183%	$40.0215	$40.02	$40.00	$40.00
Purchase #6	$85.51	10.405%	$94.4073	$94.41	$94.40	$94.40
Purchase #7	$123.45	3.490%	$127.7584	$127.76	$127.75	$127.80
7 purchase totals =	$797.06		$883.0564	$883.06	$883.05	$883.00