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	$136.28	7.758%	$146.8526	$146.85	$146.85	$146.90
Purchase #2	$185.79	12.458%	$208.9357	$208.94	$208.95	$208.90
Purchase #3	$53.46	6.374%	$56.8675	$56.87	$56.85	$56.90
Purchase #4	$55.82	11.328%	$62.1433	$62.14	$62.15	$62.10
Purchase #5	$55.37	10.766%	$61.3311	$61.33	$61.35	$61.30
Purchase #6	$169.49	13.392%	$192.1881	$192.19	$192.20	$192.20
Purchase #7	$52.35	13.255%	$59.289	$59.29	$59.30	$59.30
7 purchase totals =	$708.56		$787.6073	$787.61	$787.65	$787.60