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	$111.85	3.379%	$115.6294	$115.63	$115.65	$115.60
Purchase #2	$156.85	12.274%	$176.1018	$176.10	$176.10	$176.10
Purchase #3	$86.46	3.205%	$89.231	$89.23	$89.25	$89.20
Purchase #4	$98.99	4.296%	$103.2426	$103.24	$103.25	$103.20
Purchase #5	$21.38	13.456%	$24.2569	$24.26	$24.25	$24.30
Purchase #6	$92.44	8.538%	$100.3325	$100.33	$100.35	$100.30
Purchase #7	$139.44	3.689%	$144.5839	$144.58	$144.60	$144.60
7 purchase totals =	$707.41		$753.3781	$753.37	$753.45	$753.30