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	$200.68	5.412%	$211.5408	$211.54	$211.55	$211.50
Purchase #2	$175.85	8.448%	$190.7058	$190.71	$190.70	$190.70
Purchase #3	$71.89	9.379%	$78.6326	$78.63	$78.65	$78.60
Purchase #4	$118.86	10.528%	$131.3736	$131.37	$131.35	$131.40
Purchase #5	$112.43	6.468%	$119.702	$119.70	$119.70	$119.70
Purchase #6	$189.27	13.676%	$215.1546	$215.15	$215.15	$215.20
Purchase #7	$48.81	12.280%	$54.8039	$54.80	$54.80	$54.80
7 purchase totals =	$917.79		$1,001.9133	$1,001.90	$1,001.90	$1,001.90