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	$191.71	4.538%	$200.4098	$200.41	$200.40	$200.40
Purchase #2	$39.88	3.759%	$41.3791	$41.38	$41.40	$41.40
Purchase #3	$133.58	12.407%	$150.1533	$150.15	$150.15	$150.20
Purchase #4	$71.62	8.334%	$77.5888	$77.59	$77.60	$77.60
Purchase #5	$38.36	7.553%	$41.2573	$41.26	$41.25	$41.30
Purchase #6	$204.86	5.137%	$215.3837	$215.38	$215.40	$215.40
Purchase #7	$196.82	3.464%	$203.6378	$203.64	$203.65	$203.60
7 purchase totals =	$876.83		$929.8098	$929.81	$929.85	$929.90