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	$214.93	3.653%	$222.7814	$222.78	$222.80	$222.80
Purchase #2	$22.71	11.702%	$25.3675	$25.37	$25.35	$25.40
Purchase #3	$242.80	8.626%	$263.7439	$263.74	$263.75	$263.70
Purchase #4	$178.42	7.167%	$191.2074	$191.21	$191.20	$191.20
Purchase #5	$72.86	6.862%	$77.8597	$77.86	$77.85	$77.90
Purchase #6	$177.34	7.697%	$190.9899	$190.99	$191.00	$191.00
Purchase #7	$103.31	9.327%	$112.9457	$112.95	$112.95	$112.90
7 purchase totals =	$1,012.37		$1,084.8955	$1,084.90	$1,084.90	$1,084.90