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	$161.85	7.398%	$173.8237	$173.82	$173.80	$173.80
Purchase #2	$64.69	10.533%	$71.5038	$71.50	$71.50	$71.50
Purchase #3	$98.83	3.390%	$102.1803	$102.18	$102.20	$102.20
Purchase #4	$226.69	8.725%	$246.4687	$246.47	$246.45	$246.50
Purchase #5	$73.61	12.467%	$82.787	$82.79	$82.80	$82.80
Purchase #6	$86.50	4.788%	$90.6416	$90.64	$90.65	$90.60
Purchase #7	$227.30	8.331%	$246.2364	$246.24	$246.25	$246.20
7 purchase totals =	$939.47		$1,013.6415	$1,013.64	$1,013.65	$1,013.60