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	$247.89	3.529%	$256.638	$256.64	$256.65	$256.60
Purchase #2	$82.39	5.765%	$87.1398	$87.14	$87.15	$87.10
Purchase #3	$88.26	3.633%	$91.4665	$91.47	$91.45	$91.50
Purchase #4	$240.47	7.819%	$259.2723	$259.27	$259.25	$259.30
Purchase #5	$174.70	4.430%	$182.4392	$182.44	$182.45	$182.40
Purchase #6	$37.60	13.859%	$42.811	$42.81	$42.80	$42.80
Purchase #7	$222.63	3.648%	$230.7515	$230.75	$230.75	$230.80
7 purchase totals =	$1,093.94		$1,150.5183	$1,150.52	$1,150.50	$1,150.50