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	$156.57	10.751%	$173.4028	$173.40	$173.40	$173.40
Purchase #2	$5.39	9.697%	$5.9127	$5.91	$5.90	$5.90
Purchase #3	$11.61	13.112%	$13.1323	$13.13	$13.15	$13.10
Purchase #4	$123.88	11.203%	$137.7583	$137.76	$137.75	$137.80
Purchase #5	$159.86	3.848%	$166.0114	$166.01	$166.00	$166.00
Purchase #6	$247.78	6.730%	$264.4556	$264.46	$264.45	$264.50
Purchase #7	$115.81	13.855%	$131.8555	$131.86	$131.85	$131.90
7 purchase totals =	$820.90		$892.5286	$892.53	$892.50	$892.60