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	$58.92	10.444%	$65.0736	$65.07	$65.05	$65.10
Purchase #2	$35.76	7.191%	$38.3315	$38.33	$38.35	$38.30
Purchase #3	$123.56	10.835%	$136.9477	$136.95	$136.95	$136.90
Purchase #4	$58.61	11.666%	$65.4474	$65.45	$65.45	$65.40
Purchase #5	$32.31	6.384%	$34.3727	$34.37	$34.35	$34.40
Purchase #6	$215.84	3.159%	$222.6584	$222.66	$222.65	$222.70
Purchase #7	$54.54	13.711%	$62.018	$62.02	$62.00	$62.00
7 purchase totals =	$579.54		$624.8493	$624.85	$624.80	$624.80