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	$52.39	7.146%	$56.1338	$56.13	$56.15	$56.10
Purchase #2	$174.34	4.851%	$182.7972	$182.80	$182.80	$182.80
Purchase #3	$65.45	10.220%	$72.139	$72.14	$72.15	$72.10
Purchase #4	$106.34	5.783%	$112.4896	$112.49	$112.50	$112.50
Purchase #5	$50.74	5.149%	$53.3526	$53.35	$53.35	$53.40
Purchase #6	$87.40	5.734%	$92.4115	$92.41	$92.40	$92.40
Purchase #7	$199.79	4.672%	$209.1242	$209.12	$209.10	$209.10
7 purchase totals =	$736.45		$778.4479	$778.44	$778.45	$778.40