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	$57.87	13.498%	$65.6813	$65.68	$65.70	$65.70
Purchase #2	$227.57	11.861%	$254.5621	$254.56	$254.55	$254.60
Purchase #3	$34.58	11.208%	$38.4557	$38.46	$38.45	$38.50
Purchase #4	$19.53	12.438%	$21.9591	$21.96	$21.95	$22.00
Purchase #5	$196.58	8.506%	$213.3011	$213.30	$213.30	$213.30
Purchase #6	$34.30	12.121%	$38.4575	$38.46	$38.45	$38.50
Purchase #7	$68.96	4.742%	$72.2301	$72.23	$72.25	$72.20
7 purchase totals =	$639.39		$704.6469	$704.65	$704.65	$704.80