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	$226.71	12.299%	$254.5931	$254.59	$254.60	$254.60
Purchase #2	$191.46	3.728%	$198.5976	$198.60	$198.60	$198.60
Purchase #3	$72.83	6.713%	$77.7191	$77.72	$77.70	$77.70
Purchase #4	$68.41	7.838%	$73.772	$73.77	$73.75	$73.80
Purchase #5	$190.27	4.593%	$199.0091	$199.01	$199.00	$199.00
Purchase #6	$31.95	4.222%	$33.2989	$33.30	$33.30	$33.30
Purchase #7	$48.71	13.563%	$55.3165	$55.32	$55.30	$55.30
7 purchase totals =	$830.34		$892.3063	$892.31	$892.25	$892.30