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	$211.61	7.507%	$227.4956	$227.50	$227.50	$227.50
Purchase #2	$145.68	4.236%	$151.851	$151.85	$151.85	$151.90
Purchase #3	$78.77	3.362%	$81.4182	$81.42	$81.40	$81.40
Purchase #4	$24.83	12.745%	$27.9946	$27.99	$28.00	$28.00
Purchase #5	$101.35	10.328%	$111.8174	$111.82	$111.80	$111.80
Purchase #6	$130.25	10.697%	$144.1828	$144.18	$144.20	$144.20
Purchase #7	$165.98	8.827%	$180.6311	$180.63	$180.65	$180.60
7 purchase totals =	$858.47		$925.3907	$925.39	$925.40	$925.40