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	$158.44	11.264%	$176.2867	$176.29	$176.30	$176.30
Purchase #2	$68.56	13.185%	$77.5996	$77.60	$77.60	$77.60
Purchase #3	$172.86	12.614%	$194.6646	$194.66	$194.65	$194.70
Purchase #4	$83.51	7.231%	$89.5486	$89.55	$89.55	$89.50
Purchase #5	$155.54	12.436%	$174.883	$174.88	$174.90	$174.90
Purchase #6	$152.97	12.861%	$172.6435	$172.64	$172.65	$172.60
Purchase #7	$12.56	5.736%	$13.2804	$13.28	$13.30	$13.30
7 purchase totals =	$804.44		$898.9064	$898.90	$898.95	$898.90