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	$236.48	4.665%	$247.5118	$247.51	$247.50	$247.50
Purchase #2	$250.93	11.632%	$280.1182	$280.12	$280.10	$280.10
Purchase #3	$91.45	13.133%	$103.4601	$103.46	$103.45	$103.50
Purchase #4	$45.49	4.405%	$47.4938	$47.49	$47.50	$47.50
Purchase #5	$47.75	13.198%	$54.052	$54.05	$54.05	$54.10
Purchase #6	$197.52	6.425%	$210.2107	$210.21	$210.20	$210.20
Purchase #7	$215.34	3.447%	$222.7628	$222.76	$222.75	$222.80
7 purchase totals =	$1,084.96		$1,165.6094	$1,165.60	$1,165.55	$1,165.70