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	$139.69	4.220%	$145.5849	$145.58	$145.60	$145.60
Purchase #2	$91.71	7.127%	$98.2462	$98.25	$98.25	$98.20
Purchase #3	$179.35	3.113%	$184.9332	$184.93	$184.95	$184.90
Purchase #4	$77.40	12.491%	$87.068	$87.07	$87.05	$87.10
Purchase #5	$227.84	12.288%	$255.837	$255.84	$255.85	$255.80
Purchase #6	$56.25	13.463%	$63.8229	$63.82	$63.80	$63.80
Purchase #7	$167.48	3.805%	$173.8526	$173.85	$173.85	$173.90
7 purchase totals =	$939.72		$1,009.3448	$1,009.34	$1,009.35	$1,009.30