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	$176.64	13.386%	$200.285	$200.29	$200.30	$200.30
Purchase #2	$128.46	10.825%	$142.3658	$142.37	$142.35	$142.40
Purchase #3	$131.65	12.853%	$148.571	$148.57	$148.55	$148.60
Purchase #4	$229.52	11.595%	$256.1328	$256.13	$256.15	$256.10
Purchase #5	$52.31	10.798%	$57.9584	$57.96	$57.95	$58.00
Purchase #6	$100.52	6.541%	$107.095	$107.10	$107.10	$107.10
Purchase #7	$225.34	3.432%	$233.0737	$233.07	$233.05	$233.10
7 purchase totals =	$1,044.44		$1,145.4817	$1,145.49	$1,145.45	$1,145.60