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	$179.86	13.563%	$204.2544	$204.25	$204.25	$204.30
Purchase #2	$156.92	10.223%	$172.9619	$172.96	$172.95	$173.00
Purchase #3	$240.98	7.154%	$258.2197	$258.22	$258.20	$258.20
Purchase #4	$103.67	3.224%	$107.0123	$107.01	$107.00	$107.00
Purchase #5	$157.66	4.332%	$164.4898	$164.49	$164.50	$164.50
Purchase #6	$39.98	3.413%	$41.3445	$41.34	$41.35	$41.30
Purchase #7	$91.70	9.426%	$100.3436	$100.34	$100.35	$100.30
7 purchase totals =	$970.77		$1,048.6262	$1,048.61	$1,048.60	$1,048.60