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	$214.45	5.166%	$225.5285	$225.53	$225.55	$225.50
Purchase #2	$29.83	5.794%	$31.5584	$31.56	$31.55	$31.60
Purchase #3	$71.48	10.398%	$78.9125	$78.91	$78.90	$78.90
Purchase #4	$31.32	12.202%	$35.1417	$35.14	$35.15	$35.10
Purchase #5	$45.75	11.318%	$50.928	$50.93	$50.95	$50.90
Purchase #6	$118.25	12.456%	$132.9792	$132.98	$133.00	$133.00
Purchase #7	$169.58	9.867%	$186.3125	$186.31	$186.30	$186.30
7 purchase totals =	$680.66		$741.3608	$741.36	$741.40	$741.30