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	$174.25	8.758%	$189.5108	$189.51	$189.50	$189.50
Purchase #2	$113.61	9.607%	$124.5245	$124.52	$124.50	$124.50
Purchase #3	$33.76	5.757%	$35.7036	$35.70	$35.70	$35.70
Purchase #4	$210.94	10.697%	$233.5043	$233.50	$233.50	$233.50
Purchase #5	$117.78	12.492%	$132.4931	$132.49	$132.50	$132.50
Purchase #6	$20.62	11.821%	$23.0575	$23.06	$23.05	$23.10
Purchase #7	$250.81	5.413%	$264.3863	$264.39	$264.40	$264.40
7 purchase totals =	$921.77		$1,003.1801	$1,003.17	$1,003.15	$1,003.20