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	$137.86	4.767%	$144.4318	$144.43	$144.45	$144.40
Purchase #2	$107.81	7.464%	$115.8569	$115.86	$115.85	$115.90
Purchase #3	$54.84	10.517%	$60.6075	$60.61	$60.60	$60.60
Purchase #4	$240.83	3.862%	$250.1309	$250.13	$250.15	$250.10
Purchase #5	$100.84	8.692%	$109.605	$109.61	$109.60	$109.60
Purchase #6	$224.31	11.200%	$249.4327	$249.43	$249.45	$249.40
Purchase #7	$106.64	6.820%	$113.9128	$113.91	$113.90	$113.90
7 purchase totals =	$973.13		$1,043.9776	$1,043.98	$1,044.00	$1,043.90