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	$133.90	5.418%	$141.1547	$141.15	$141.15	$141.20
Purchase #2	$78.33	5.522%	$82.6554	$82.66	$82.65	$82.70
Purchase #3	$247.38	5.210%	$260.2685	$260.27	$260.25	$260.30
Purchase #4	$52.57	12.600%	$59.1938	$59.19	$59.20	$59.20
Purchase #5	$200.96	4.352%	$209.7058	$209.71	$209.70	$209.70
Purchase #6	$129.60	3.430%	$134.0453	$134.05	$134.05	$134.00
Purchase #7	$148.78	5.132%	$156.4154	$156.42	$156.40	$156.40
7 purchase totals =	$991.52		$1,043.4389	$1,043.45	$1,043.40	$1,043.50