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	$177.72	13.275%	$201.3123	$201.31	$201.30	$201.30
Purchase #2	$137.53	11.241%	$152.9897	$152.99	$153.00	$153.00
Purchase #3	$56.82	5.211%	$59.7809	$59.78	$59.80	$59.80
Purchase #4	$148.64	10.800%	$164.6931	$164.69	$164.70	$164.70
Purchase #5	$215.54	5.856%	$228.162	$228.16	$228.15	$228.20
Purchase #6	$119.71	6.704%	$127.7354	$127.74	$127.75	$127.70
Purchase #7	$202.82	6.326%	$215.6504	$215.65	$215.65	$215.70
7 purchase totals =	$1,058.78		$1,150.3238	$1,150.32	$1,150.35	$1,150.40