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	$131.86	7.720%	$142.0396	$142.04	$142.05	$142.00
Purchase #2	$79.86	13.211%	$90.4103	$90.41	$90.40	$90.40
Purchase #3	$88.86	12.252%	$99.7471	$99.75	$99.75	$99.70
Purchase #4	$59.83	5.210%	$62.9471	$62.95	$62.95	$62.90
Purchase #5	$200.59	6.328%	$213.2833	$213.28	$213.30	$213.30
Purchase #6	$228.28	13.461%	$259.0088	$259.01	$259.00	$259.00
Purchase #7	$81.27	10.780%	$90.0309	$90.03	$90.05	$90.00
7 purchase totals =	$870.55		$957.4671	$957.47	$957.50	$957.30