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	$150.41	10.706%	$166.5129	$166.51	$166.50	$166.50
Purchase #2	$236.47	10.233%	$260.668	$260.67	$260.65	$260.70
Purchase #3	$176.35	11.649%	$196.893	$196.89	$196.90	$196.90
Purchase #4	$79.39	5.716%	$83.9279	$83.93	$83.95	$83.90
Purchase #5	$132.56	4.773%	$138.8871	$138.89	$138.90	$138.90
Purchase #6	$61.75	4.517%	$64.5392	$64.54	$64.55	$64.50
Purchase #7	$218.61	10.598%	$241.7783	$241.78	$241.80	$241.80
7 purchase totals =	$1,055.54		$1,153.2064	$1,153.21	$1,153.25	$1,153.20