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	$118.75	12.758%	$133.9001	$133.90	$133.90	$133.90
Purchase #2	$100.69	10.563%	$111.3259	$111.33	$111.35	$111.30
Purchase #3	$47.62	11.492%	$53.0925	$53.09	$53.10	$53.10
Purchase #4	$112.83	5.817%	$119.3933	$119.39	$119.40	$119.40
Purchase #5	$120.95	10.249%	$133.3462	$133.35	$133.35	$133.30
Purchase #6	$136.82	13.358%	$155.0964	$155.10	$155.10	$155.10
Purchase #7	$212.77	12.163%	$238.6492	$238.65	$238.65	$238.60
7 purchase totals =	$850.43		$944.8036	$944.81	$944.85	$944.70