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	$136.64	5.193%	$143.7357	$143.74	$143.75	$143.70
Purchase #2	$59.77	4.389%	$62.3933	$62.39	$62.40	$62.40
Purchase #3	$38.84	12.533%	$43.7078	$43.71	$43.70	$43.70
Purchase #4	$37.50	4.436%	$39.1635	$39.16	$39.15	$39.20
Purchase #5	$71.37	10.367%	$78.7689	$78.77	$78.75	$78.80
Purchase #6	$16.76	3.550%	$17.355	$17.36	$17.35	$17.40
Purchase #7	$194.66	12.586%	$219.1599	$219.16	$219.15	$219.20
7 purchase totals =	$555.54		$604.2841	$604.29	$604.25	$604.40