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	$122.64	7.470%	$131.8012	$131.80	$131.80	$131.80
Purchase #2	$38.98	9.545%	$42.7006	$42.70	$42.70	$42.70
Purchase #3	$52.63	7.613%	$56.6367	$56.64	$56.65	$56.60
Purchase #4	$73.65	5.784%	$77.9099	$77.91	$77.90	$77.90
Purchase #5	$60.33	11.194%	$67.0833	$67.08	$67.10	$67.10
Purchase #6	$168.81	6.785%	$180.2638	$180.26	$180.25	$180.30
Purchase #7	$137.61	3.476%	$142.3933	$142.39	$142.40	$142.40
7 purchase totals =	$654.65		$698.7888	$698.78	$698.80	$698.80